replaced mine recently from OE diaphragm to new style piston, no change in performance for me
10,000 miles as OE map, 30,000 miles on APR stg1 (total 40k miles +) and it was still intact
but changed anyway as its a better design.
bottom line is that if you have an early version it 'may' tear at some point but it doesnt necessarily mean it has.
On a K04 car is a no brainer as its so easy. For the sake of £50 its worth changing it
and if you have a K03 and performance isnt great then def be the first place to look (VCDS to confirm, as the K03 location is a bugger to change)
not a forge fan to be honest when the updated VW design seems to work
(and its OE and simplier to fit)