I need your help.

we've planned out our solar system and the battery bank seems to suit our charge controller, pure sinewave inverter, solar panels. But i was wondering about the down side to doubling the number batteries we have, and this is why.

The set up is at our cabin. we're not there all the time. When we ARE there we are very careful about our electricity usage, but even being so careful our battery bank is only large enough to last 2.5 day. if we over-sized our battery bank, all those batteries could be charging while we're away and we'll have more stored energy to use when we are there.

so what are the down sides (besides the financial commitment of purchasing the batteries and related set up technology)?

thank you for your help