If you do an internet search, you can find some pretty good advice about how to manage a 12v house bank. From what I recall, in a nutshell:
1) The less deeply you discharge, the longer the life.
2) Discharging 100% (whatever that means -- I think down to 10.8 volts) is near instant death to lead acid batteries.
3) Damaged and even dead batteries can be substantially restored, at least a few times, by "equalizing", a process that requires a charger with that function.
4) The more fully-charged a battery is, the slower it will charge; ie, recharging a battery from 50% charge to 75% charge is WAY faster than recharging from 75% to 100%.
5) In balancing competing demands (primarily, house bank size, recharge time and battery life), many people adopt a 50% approach. The run the batteries down to a 25% charge, then charge back up to 75% and stop there in order to not continue to run the gen set. I used that approach for years on my boat and got 4-5 years life out of the batteries, "equalizing" the batteries about once a year.
6) A good state of charge meter (which will include a bunch of useful ancillary functions) is necessary to maximizing the efficiency of your house system. I used a Link 30 (maybe 20) and liked it alot. Come to think of it, they had (still have?) very useful materials on line.