What am I doing wrong?

I've had multiple Macs and all of them have lasted longer than 3 years. Shrug.

 

The 2 laptops can be understood. The Tower and the iMac are more surprising.
I've had four to date beginning with a 1984 era Apple IIc. All four are still operational. No laptops amongst the group. All the laptops were PC based. Granted on the G5 1.8 Tower I've updated the hard drives and jockeyed memory, etc. Been fortunate for some reason.

So many variables. Hard to say. Try giving your next one a name and a tickle now and then.

 

Apple II+, Apple IIe, various Powerbooks, Macbook Pros, Mac Pros...

So far I've lost 1 hard drive, and that was on a 5 year old Powerbook.

 

Only you can answer that question.

 

Keep The Junk Out

By running disk utility or Onyx from time to time.....You don't say what your others actually died of HDD? RAM? I fully expect this iMac, my latest to last me out.

I specced up...I7 16GB RAM 2GB graphics....It flies. Also Apple do recommend that you leave your machine on, thus allowing it to run scripts etc.