You should be able to get a couple of years out of the. For some, they may last longer and others maybe less. It helps to not over tighten them as it doesn't take much to keep them in place.
I have tried every type of rubber that could possibly work for those straps and always end up back where I started. The new straps are slightly thicker and black and seem to last longer.
Some types of rubber damages the bow finish and other rubber is not strong enough. Unfortunatly, any type of rubber that will grip the limbs as well will typically only last a couple of years. We sell replacement straps and they are resonable.
thanks, bigjim