The problem is only solved with the successor, the True Wireless 2. The earphones no longer empty out in a few days. Even after a good 2 weeks of non-use, they are still full. Unfortunately, there is no solution for the predecessor. You have to live with it, i.e. permanently plugged into the power supply, or buy the successor.

No, no firmware update, no software update, nada...
Is only for frequent users no problem, if you want to use the headphones once a week, they are usually empty.... if not constantly on the charging cable.
If you use them every day anyway, it's less of a problem.

The problem seems familiar to me. I have now changed to Aeropex Aftershokz, which solved all my problems. It is disappointing that the renowned company Sennheiser does not have a better product.