Realisticly, it doesn't matter. As it is -not being used- when your device is running on AC and not charging, it shouldn't go down much. Perhaps a couple %/day.

Also, the battery monitor is rough, at best. It can often be 10+% off!

Once in a while, you should run it completely out, and then charge it up fully. That will reset the monitor, and should provide a (more)accurate reading.

If you are finding that you aren't getting much battery life(regardless of what it -says-), you probably need to replace your battery.

When it has reached full and green light, the indicators never switch back to yellow/charging again, but the actual top-up charge does take place periodically. Tested and measured through bq27200.

"Never" meaning I've only ever once seen it switch back to indicate charging.

I don't think it takes energy directly from the wall