I agree with the others, based on the data you've given so far. But you're right that batteries should last longer.
What voltage did you charge the batteries to?
You call them "GSM" batteries - are these the same as AGM
? Although this whole business is an alphabet soup, GSM is a type of phone
signal to me. The normal types of batteries (that I know about) are Wet (sealed or not), Gel, & AGM
, with a few LiFePo (but they're very special cases). Wet cells are the most robust, & can take significant abuse, but Gel & AGM have special charging
requirements. Specifically, if you take them to too high a voltage (which is temperature dependent) then you can kill them very quickly.
Taking 175Ah out of a 625Ah bank is bringing it down to 72%. A high quality deep-cycle battery should do that many times. But just for reference, we also have a 660Ah house bank, & only rarely do we take more than 100Ah out of it (but we have a large solar
array to keep it topped up).