Hi Mike,
Well I don't change mine very often, only every 5 years or so, although I don't know how much of a reccomendation that is! I've never had any problems.
If they are still in good condition then just give them a good wash- with some softener- in the washing machine, they're quite expensive things to replace if they are just a bit stiff.
I only change mine after a period of extreme wear, and when they start to look tired, so if you don't use them much then really don't worry too much about it- unless they look tired.
I'd stick them in the wash first and then see what the result is like!
J