Hey Kanga Man, the Exo Pro have undergone a long test period, the guys that were testing them did so for over 6 months and in that time they didnt need to replace them. This does all depend on how you are using them and if you are a frequent user I would suggest keeping them maintained well and change them 2 - 3 times a year. The Quick Release metal clamps have also been tested to the max and no failures as yet.
I have to reiterate though that these stilts are not service free, the better you look after them the more you will get from them and the longer they will last.