One evening, I set my pipe down with about 1/4 of a bowl of LBF left over. The next morning, I knew I'd have time for a full bowl. The pipe was completely cool by then, of course. I was in the mood for PA, but instead of scooping out the remaining LBF, I tapped the ash out, and topped off the bowl with the PA. It smoked without any difficulty, and I didn't notice anything odd about the flavor. I rather enjoyed the sudden transition when I reached the LBF at the bottom.
Is there anything wrong with combining fresh and burnt tobacco like this?