My Mom's iMac is on its last legs. I think I got it for her in early 2006 and its screen is having some streaking problems. Otherwise it still works, but a lot of the latest Apple software won't load on it. ...
I'd be pretty ticked if my 4+ year old, $1300+ personal computer was a)having screen problems and b)was basically on it's last leg.
Every single Wintel and Mac machines I buy last at least 5 years...a high percentage of them last until 10 but by then they are so old it's almost pointless (such as only having USB 1.1 ports or old screen resolutions or floppy drives or small storage space) even though they run just fine.
You might want to spend $200 and see if it's just a memory and/or general performance problem that you can fix yourself.