When you get HBD from post rewards, this is part of the normal hive inflation which is at around 7-8% at the moment. The interests on HBD is in addition to that and the more HBD is in savings, the higher the inflation will be.
I'm doing the same than you. I put my HBD in savings and still comment and curate but there are other people who just gave up on it and put all their money into hbd savings. Like that they get a fix return that is higher than what they would get with HP.
Well, I don't know them. They're probably some kind of whales. But they make their money from delegation and automatic upvotes anyway.
I only know people like you and me who are doing something with posts, comments, and something in savings.
Well, maybe we could also comment on "normal Hive inflation". It's based on some calculations, surely, just like HBD savings...