[Closed] Knee pads, how often to replace them?

I've got a set of Leatt Airflex Pro's, done the job well over the last couple of years, but in the last few rides the bottom of the rubber protection has been curling in and digging into my lower shin, which is a bit uncomfortable on rides of more than an hour, especially as any rejigging of the pads doesn't really do anything.

So i take it the moulds can lose shape, and need replacing, or is there a way of getting it back, i've bent it round, will try a bit of heat, and may even try a bit of foam around it, as it's the bottom of the pad, but, if it's not good, what are the 'in' pads to choose these days ;o)