Last trip was our first time on the QSDP (had always done the regular DP previously) and we did NOT eat any TS and still had credits left over.
That being said, we have 2 ADR's next month while on the (free) QSDP. One ressie is to meet old friends who live in NC but will be visiting Disney at the same time so we are meeting for dinner. The other ADR is "just in case", we may end up cancelling because it's at the end of our trip, is Coral Reef, just because we enjoy eating there.
I'm sure we will have way too many credits left at the end of our trip but since we didn't pay for QSDP, I don't feel obligated to "get our money's worth". Yes, we could have upgraded to the regular DP by paying the difference but we didn't want to be tied down to a bunch of ADR's during FD.