Sounds pretty normal to me. We do BLS, but DS is always in the high chair for at least 30 mins at each meal. From what I know the LO's are pretty good at letting us know when they're done, not opening the mouth is a good sign. I tend to think that as long as he's happy to take it, keep giving it. You'll probably find sooner or later that you'll have meals where he'll refuse to eat anything (now that is hardwork!).