My previous IBM ThinkPad is approaching 7 years old and still doing good service on daughter's boat (don't ask!). There's no reason any part other than battery or hard drive should die.
I don't know your specific device, but I've got batteries for the ThinkPad (old and new) off Ebay for under £40. If the performance is adequate, I'd treat it to a new battery (<£40) and a new HD (also <£40), and be happy.