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If it's the computer, your budget will decide if you want to treat yourself to another computer or not. If money is tight, and the computer basically works for what you want it to do, you seem to have worked out a strategy for checking the battery. Maybe just change it a bit more frequently (the kits are about $20, right?). I agree, that sounds frustrating.
I don't have sufficient self-confidence to change the battery myself. I send it to Dive Supply here in Thailand. That costs me almost a hundred bucks (US). That means it costs between one and two dollars per dive for the battery. That seems high to me.