My son first lost one 1month after start. Then lost 2nd time but searched and found. This year he lost one as 3rd time. So in most chance, I prepare for lost case.
In summer, the dirty lens can cause red-eye. We have eye-drops ready for this case. In worst case, I also have the doctor to deep clean lens to get it back to normal.
So we have the CRT lens for 8yrs w/o change. I'm a cheap mom :-)