I have 4 200Ah Narada MPG batteries connected with Infini Plus 10KW. In my area we get frequent blackouts (typically 3-4 hours per day, around 4 days a week). Couple of things I've noticed is when there isn't any blackout for a day or two, the batteries are still continuously charging (floating charging) at 2.1 amps and battery capacity is always at 99% (as per inverter).

In the settings there is an option to stop charging after X hours if the amps is less than Y. I was thinking of setting it to 24 hours and 2.1 amps. Does that sound like a good idea?

Victron inverters have something called storage mode. It drops the voltage by another small increment after 24 hours, or as an example: If you float at 55.2V, it will drop the float voltage to 52.8V after a day.

This is a non-gassing voltage, so it does stop charging the batteries, and it still prevents self-discharge to some extent (though not completely).

If you can set the inverter up to to an absorption run once a week it works perfectly. If not, then self-discharge will set in and draw the batteries down.

I think it is a good idea you could bring it down to 16 or even 12 hours.