Depends.......
What do you have as 'charger' (Converter----Inverter) and how 'smart' is it?
My converter is 3 stage but my inverter is 'smarter' so I use the inverter.
My 50A 5th wheel with dual 12V batteries is always plugged in at home.
At first I checked batteries weekly for any signs of overcharging-----specific gravity per cell, levels in each cell, signs of 'moisture' on battery tops etc.
After several weekly checks I then went to monthly checks...then every 3 months.
Good charger/charging system----no boiling of batteries then YES plug in and keep batteries maintained
And don't forget to level rig so you can run fridge too.
Nice to have COLD beverages etc in the 'man cave'