Now...when our DS was just past 2 into 3 years, we had the tickets, but they didn't ask for them. He was a preemie and is still at the 5th % of the growth chart, so he is smaller than others his age. He also was not allowed to ride many of the rides that taller kids his age were able to ride (that was really hard). So, we forgot the first time to give the CM his ticket, then we found he wasn't doing anything more, different, better then when he was 1 and 2 years old and basically justified the non-usage of his ticket for that trip.
I drew the line at that trip (I think he was 3 yrs and 3 months old or something like that). The next trip, we did use the tickets and of course have ever since. Also, I actually looked at the height requirements for his rides and made sure that he was tall enough or projected that he would be tall enough at the next trip. For us, there was no point in going back until he was tall enough to do Star Tours, and Stitch's Great Escape (things he was told he couldn't ride that one year). If our child isn't having fun, then we aren't going to go to WDW.
Now, ever since, we have big fun before the trip measuring height, looking up rides to see if there is one that he couldn't get on before and can now. The last few trips it was Big Thunder MR. We rode that thing over and over again - he had so much fun!
Wow what a long answer to a short question!