Q: Is neoprene like a kind of rubber? Does it become stiff over time? If yes, best use within how many years?
A: Neoprene does come from the family of synthetic rubbers so technically it is a rubber but it resists degradation more than regular natural or synthetic rubbers. This means that it does get stiffer over time but not as fast as regular rubber. It is hard to say how many years it lasts because the degradation happens gradually and it also depends on the use – especially how much exposure to sun and UV rays the material has received.
So how long does a wetsuit last? In practice often other problems appear first – like the seams falling apart or neoprene becoming to loose and stretched out from the use. Also cheaper more stiff neoprene lasts longer than high performance extra stretchy one. All this taken into account a high performance wetsuit should last at least 1-2 seasons and a more durable in stiffer wetsuit should last at least 3-5 seasons.