A solidly built wooden bed could last for many centuries.
e.g:
http://riverwoodbeds.co.uk/wp-content/uploads/2012/09/riverwood-oak-bed-027large.jpg
Even my ultra-cheapo pine bed has lasted nearly a quarter of a century since I bought it, and it was secondhand then! (I'd still expect it to go on lasting far longer than I will).
Divan beds are likely to have far shorter liftimes.
e.g:
http://www.sterlingbeds.co.uk/images/paris_divan.jpg
That's because the fabric around the sides tends to get worn or come away. Also the top is often made of fairly flimsy wood, which bends or splits. Even so, a 'cheapo' divan bed should probably last at least a decade, while a good quality one could last for twice as long.
The Sleep Council (which is funded by the trade association for bed manufacturers and so has a vested interest in persuading people to buy new beds and mattresses more often) suggests that people replace their beds (not just their mattresses) every seven years. Many (most?) people would probably consider that to be more often than necessary for divan beds and totally ridiculous for the type of bed in my first link above!
However 5 to 7 years is often quoted as the lifetime of a mattress and many people might agree with that estimate. Even so, I purchased my current mattress secondhand many years ago and it's still really comfortable. It's on a pine bed frame, so it's well supported underneath, and it's got an old duvet folded up on top of it (under the bed sheet) so that it feels really comfortable. Like my bed, I'm reasonably confident that it will 'see me out' ;-)