For the record, I don't like level caps either. If I stuck level caps on my gaming because of what I expected to happen over the last 27 years, a few games would have never gone where they did, let alone last as long as they did.
So I say go with level 20, or even 30, or even 100 caps. IF you end before level 11, fine. IF your game and group lasts long enough to go to some point beyond level 10, so much the better.
The only reason I bought into the DCC RPG even with its level caps is because I see it looking pretty easy to develop it past that cap if I ever need to, and I bet Joe is going to eventually offer a supplement to take it past level 10 as well.