I doubt that it would ever come to a meltdown situation, I think there is a lot of fear about batteries that is not justified unless you do something very silly, but preventing destructive discharge in event of a cell failure is sensible.

over time the self discharge which just like regular discharging will build up some sulfation and over 4 months is likely to harden and become difficult to break back down on recharge.

the result is loss of capacity.

some battery technologies are worse than others when it comes to self discharge.
the higher the antimony content in the plates the higher the self discharge rate.

iirc figure on about 2% per month, which compounds like interest monthly (maybe), and likely will be higher as the batteries get older.

at the very least i would make a good log of specific gravity readings if they are flooded cells, and then upon return be prepared to fully charge them and if necessary do an equalization charge to get them back into proper condition.

how big of a bank do you have? what type of battery technology? agm, flooded,vrla, etc.. ?

each have their own concerns.

  Instead of just switches, you could put in a switch and fused link in parallel on each bank to prevent a melt down, and still be able to maintain the battery bank while you are away. When the switch is open, the power will go by way of the fused link. Just a thought.