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I find that I start lusting for new hardware somewhere around year two, but resist until somewhere around year three.

I'm desperate to replace my PowerMac G5 (31 months old) with a new Mac Pro. I'm still quite happy with my MacBook Pro (16 months old).
 
I try around tax return time, last year I got a new iMac this year Im looking at the new SR MacBook.
 
Every 2-3 years or so. I replaced my 15" PB after 3 faithful years of service with a 15" MBP. I replaced my aging G4 tower with a macpro last year after 4 years of service.
 
Apple IIe: Age 12
Macintosh Classic LC: Age 19
Performa 61xx CD: Age 24
G4 450: Age 28
2.8 24" iMac: Age 36

5 Apple Computers in 24 years, 4 Macs in 17 years, but I guess the frequency picked up a little. I kept my G4 forever though. Just sold it last month to a Linux guy who wants to mess around with OS X. It's still going.
 
Apple IIe: Age 12
Macintosh Classic LC: Age 19
Performa 61xx CD: Age 24
G4 450: Age 28
2.8 24" iMac: Age 36

5 Apple Computers in 24 years, 4 Macs in 17 years, but I guess the frequency picked up a little. I kept my G4 forever though. Just sold it last month to a Linux guy who wants to mess around with OS X. It's still going.

wow, I don't think I could wait that long
 
My first Mac was a G4 Mini in April '05. Since then I've had a CD Blackbook, CD iMac, CD Mini and now a C2D MacBook.

In January I'll get a MBP, so that'll be six machines in just under 3 years! (I only own one machine at a time though, selling the old model)
 
I seem to upgrade my desktop and laptop machines every four years or so. Got my G5 in 2004 and my 12" Powerbook in 2005, so I'm about to hit my upgrade cycles again.

So I'm just waiting for the new Mac Pro models to hit.
 
I bought my iMac in August 2007, my previous Windows desktop was purchased in February 2003, so about 4.5 years.
 
I don't really care about having the "latest and greatest." My wife and I had two PC desktops. Our first one we got in 1999, the second in 2003. We just recently each got our own laptops this month, a MacBook for me and Dell Inspiron for her. Ideally, we will both have these notebooks for a good 5 years.
 
PB Pismo - 5 yrs.
17" PB - 2 yrs

Now I have the 17" MBP C2D. I will probably keep it till it dies or give it to my wife and update in a year or so...

Nuc
 
I don't have record, Got a iMac 17" in mid 2006, then family bought a macbook for on vacation, but grandfather needed computer so, mid 2007 my 17" went to him and i got the Macbook, now my question is:

what's the best A iMac 17" from mid 2006 with Core duo 512 MB ram or a
Macbook 13" mid 2007 Core 2 duo , 512 MB ram, I prefer the Imac because of the big screen, but the macbook is slightly faster, wich would you prefer?
 
My current PC was purchased in 2002. It was still running fine and has never had any problems. It is just getting a bit slow so it was finally time to upgrade. I just ordered a 24" imac last week.
 
Every 2-3 years or so I get a new machine.

iMac - Oct 2002
PowerBook - Aug 2004
PowerMac - April 2005
HTPC - Aug 2007

Actually I'm due up for a new Mac ....
*shakes fist at Steve* Where's my ultraportable!!
 
I usually replace my desktop about every 4-5 years. I keep my laptop longer since I only use it for e-mail and a few other things when traveling. I bought a G5 tower when they first came out and now have a new iMac. I started out with the original Apple II with 48k memory! 🙂
 
I was hoping to add a MacPro by springtime next year. That will make my PB 36 months old if I buy it in March. So not replacing just adding to the family.
 
how often new mac

about every 5 years - keep undating as it ages - then pass it on to a relative who is less likely to purchase new
currently own 2 - g5 and mb

love my macs
 
][+ 1979
][GS 1986
Parents "switched" to PCs 1990 😱
(Got tired of driving their computer to my friend's house to fix it every few weeks, got myself a Mac.)
iMac DV 400mhz grape 1999
Cube 450mhz 2001
G5 iMac 20" 1.8ghz (refurb.) 2005 - current
MacBook CD 2.0 ghz (refurb.) 2006 - current

Note that my parents and sister switched back shortly after I got my iMac.

*If you want to stay on the leading edge, buy refurbs - you can literally get a new computer every year and sell what you have for damn near what you paid. 😉
 
][+ 1979
][GS 1986
Parents "switched" to PCs 1990 😱
(Got tired of driving their computer to my friend's house to fix it every few weeks, got myself a Mac.)
iMac DV 400mhz grape 1999
Cube 450mhz 2001
G5 iMac 20" 1.8ghz (refurb.) 2005 - current
MacBook CD 2.0 ghz (refurb.) 2006 - current

Note that my parents and sister switched back shortly after I got my iMac.

*If you want to stay on the leading edge, buy refurbs - you can literally get a new computer every year and sell what you have for damn near what you paid. 😉

I always wanted a iMac and mid 2006 i got one, after some months family also got an iMac and after a year bought a Macbook for vacation house, i got in meanwhile an ipod 2G and sister shuffle 1G, and now my dad has Ipod touch 16GB , we are applelating 😛
 
I bought a 15" Powerbook in March of 2005, then a 20" iMac C2D in February or 2007. I usually keep a computer 2-3 years depending on the computers performance and the new offerings. They iMac is awesome, so i'll probably upgrade it in a year or so, the Powerbook will prob get upgraded around tax return time.
 
I too am still on my first Mac, a Rev A iMac G5, that I bought in Sept 2004. I recently got the upgrade bug, but rather than shell out the bucks for a new machine, I spent about $200 maxing out the RAM to 2 GB and adding a 500 GB HDD (was running with 768 MB and 160 GB before). Hopefully, these upgrades will hold me another year or so, and then I'll get a new one. Maybe adding Leopard will help me hold out even longer.

I'll probably go Macbook or Macbook Pro with an external monitor next time around though, but who knows what will be available when I am ready to upgrade AND can afford it.
 
Almost 2 yrs since the 15" MBP, so I'm craving for an upgrade (C2D, 4GB & FW800). Trying really hard to not buy before Jan but the urge is..so..strong.

Plus I don't like it when my work laptop (ugh Dell) is newer (not better) than what I have at home. Principles. 🙂
 
Well as of now, I am waiting until January for an updated MBP...when I get that it will have been about 6 years since I've owned a Mac...I had a G3 Green tower from 1999-2002 and I and I was being limited by software I couldn't use on the Mac OS (Virtual PC was the only way and it was terrible)...so I switched to Dell and then Sony for the past 6 years...and I am ready now to return to Apple! 🙂
 
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