Hello @valchiz
Saving in stable currency is necessary, because it is a way to protect ourselves against volatility, it is a way to back up gains, in short, and they are not going to charge you anything for having usdt or busd in Binance or Metamask, for example.
The option you are talking about in Hive, saving in HBD is a very good way to do it, you use Hive as a savings cue that generates real interest for you. That's great.