How long should an iPhone 3GS last and an Acer Aspire laptop?

I ought an iPhone 3gs 2 and a half years ago.
I bought the laptop nearly 2 years ago.

Both are in good condition, but regardless of that, when should I replace them ( because of better technology OR because of needing to replace it ) ?

Added (1). *
The laptop is slow, and the battery life of the phone is poor.

I should say you've to sell both of them. And upgrade by buying an iphone 4s or iphone 5(if you're opt to) and other than Apple, I should say Lg Google Nexus 5.
For Laptop, please go to Asus or Toshiba or Apple. Because these are have best reliability records.

It pretty much depends on what do you except from your phone and laptop. If you are gamer you will need to replace your laptop very soon. But if you only search internet and using it for school/work you don't need to change it for 5-6 years, even than it will work properly, because PC parts are made to last. About your phone… I don't see a reason to trow away your 3gs, it's very fluent phone and you can run almost all apps on it, no matter how old it is. So my advice about phone would be to stick with your phone for couple of months and wait iP6 to come out. And than because of all Apple you could find 5 or 5s for a very low price. I personally bought bad imei iPhone 5 for 150$, do I need to say more