Neoprene will naturally stiffen and even shrink as it gets older. The best thing to do for your wetsuit is to try to ensure that this process happens as slowly as possible and to mitigate the aging of your suit so that it will last as long as possible while still functioning. Here are a few tips to that end:

• Keep the suit out of direct sunlight (except when being worn, of course), as the heat and UV rays will cause cracking and stiffening.
   
• Never put a wetsuit in a dryer, and avoid exposing it to excessive heat, i.e. from a room heater or from draping it over a radiator.
   
• Rinse your suit out well after each use. Dissolved minerals in the seawater accelerate the degradation of neoprene.
   
• Keep your suit clean. If dirt or salt (see above) gets into the inner lining of the suit, it can interfere with the suits ability to trap an insulating layer of water near your skin. Some surfers use shampoo, Armor-All, or even purple bubble bath to clean their suits.
   
• Avoid purchasing a suit that is too small. Neoprene will stiffen as it is stretched repeatedly over extended periods of time.
   
• Get some neoprene glue and take some time to fix up leaks and holes before they become too large to repair.