Smartphones are not made to last. Even if the hardware can still hold up, and at least the battery will usually not, the software will be outdated.
If you expect more than two years, you should consider buying a normal phone and a computer
I sort of disagree... My Droid 2 easily lasted 2.5 years and then I sold it. My refurbished BlackBerry Bold 9000 (with a ball - not a touchpad) was a tank of a phone. Indestructible and I used it 3 years and then sold to someone. (which I really regret).
I think a quality phone must last at least 3-4 years with no issues. I don't mean it should remain competitive with whats in the market(which would be impossible) what I mean is, it should remain in working order. If a phone cant do that, it's not a quality phone and not one I would buy.
The phone in the OP, HTC desire, is a crappy phone IMO. Maybe ok for a non-poweruser but I'd never buy it. It's one of those.. Entry level/budget phones. Even an old iPhone would be a much better investment... or even a Samsung Captivate...
Here's a snippet of a quote for gsmarena:
"... i have this phone but seriously this is a shitty phone full of problems heating problems,low internal memory ,bad camera ,no over the air update to 2.3,less mb of ram only 570 or something like that. its just not worth buying this phone..."
When you get a smartphone, either buy the best, buy used, or get a flip-phone. Those hardly ever fail. There is no "getting a smartphone on the budget" type of thing when it comes to smartphones.