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I leave mine on for about 5 days at a time, then usually restart on the weekends.

Matt...
 
I'm currently at 28 days and 5 hours. Guess that means I last rebooted around New Year's Eve. Going to see if I can get a year's worth of uptime, just for kicks.

Oh, and I'm running 10.4.11.
 
I use fan control and set the temps and fans speeds. LCD turns off after certain time and with that, it is on for weeks on end.
 
Mine only get rebooted for updates, and has been on for several days at a stretch without even sleep mode.

I've always treated my Macs this way (desktops and laptops) and have never had a problem.
 
Longest I have had it on is maybe a little under twenty four hours. I'll normally shut down my laptop when I am not using it.
 
I leave mine on all the time, but I do let it sleep when I'm not using it. The occasional reboot when Software Update asks for it and when things go nuts.

Current uptime is just over 9 days. Though it's been up for longer than that before.
 
Currently

Code:
tim-crosss-macbook:~ Tim$ uptime
22:42  up 4 days,  3:09, 2 users, load averages: 0.40 0.69 0.89
tim-crosss-macbook:~ Tim$

I had a KP a few days ago - had been up since the MWSF updates. I never turn it off by choice.
 
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