Jack has worn his for over 6 years and we are on our third pair. I don't remember it being specificly 2 years, as he has grown in spurts. It has been as needed, we take them with us to our appointments every 6 months to make sure they still fit well, etc.
We are almost in need of our second pair. We just had the calf part adjusted/widened because he got taller and the straps were now lower on his big calf. Our PT said usually every 6months you need a new pair, especially when they are little and going through frequent groth spurts.
My son is 7.6 yrs old, yet he doesn't have night splints because NO body from the medical staff told us that he need one,I will call his dr to ask him for splints I'm sure they will be helpfull for him.
With the last two hospital we been,I think that you have to ask them first about everything THEN they will say OK,it suppose to be the other way...!!??
Joshua is coming 6 now and is on his third pair. We don't have a regular appointment to get them checked, but each year we go to his annual appointment with his 4 doctors, we take his boots along and have them checked. In between though, if his toes are getting too close to the end, just like regular shoes, I lay him down and see where they come to. If they touch the end, we make an appointment and go have some new ones made. It takes about 6 weeks to get the boots made and ready to pick up. We don't have to pay for them even if his feet grow out of them twice per year.