A late but added note you may be able to use?
Remember, not all chargers are created equal. Cheap ones sometimes boil the battery to death.
Once a plate is exposed by any method, that cell is essentially dead so ensure you check them regularly. Some chargers are not smart enough to distinguish between full and partial charges, or for that matter, or empty <=50%.
You should note that different batteries, wet cells, GEL, AGM, and so on take different charge loads and voltages. Charging GELs with wet cell voltages and currents may bulge the battery and render it/them useless.
Further notes: if you have 2 batteries of different capacities or charges you may find one battery compensating for the other leading to a more rapid discharge in both, etc.
And to your question: as the former and last answer suggested keeping a charge is important no matter where your battery is. I keep mine in the basement also on wood blocks for simplicity. It's cold out there you know?
All batteries discharge over time, especially those which are dirty on its surface. Batteries left in your rig may also power stuff in that rig. The only way some people know something might be on is with an ammeter, but that's another story.
Finally, a friend of mine has a converter which is NOT a 3-stage unit. Perhaps, like he does, charging for a short period, say 15 min per day, is an alternative to costly upgrades? I do this even with my good converter, but I'm one who hates to buy batteries and, who knows? However, my chargers are all smart, 3-stage, with monitors.
You be the judge.