mrbb is correct that sun an UV light can weaken straps. However most mfgrs. of tree stands and steps use straps that are protected against UV light. DO NOT use those camo straps from Wlamart or other places that sell them. They are not treated for UV protection and will loose their strength quickly. Here in PA we cannot use any items on public property that damage the tree. This would include bolt on steps. Check your regs.
Edit: Its a good idea to purchase replacement straps for your stands and sticks every couple years.