Q: 2 1/2 year old battry not holding charge when not used for a week

My van kills a battery every 3 years or so, I seem to have to replace it every 2 1/2-3 years, usually when it's still under warranty it happens so quick. I'm on the 4th one at this point, and this one isn't dead, dead like past ones but it's acting strange. If i drive daily, or every other day, it's fine, no stalling, no issues, voltage reads fine when running. Recently I've started to carpool to work, and now every week when its my turn to drive, the battery is dead, and I have to check/charge it the day before, or jump-start it the morning of. Once I do that it's good, until it sits for a week not driven. Alternator was replaced around 5 or so years ago, and it does charge when running (used a volt meter on it to check)

All inside lights have been manually turned off, to make sure there isn't a short there, headlights aren't on, ect. Even disconnected my wiring harness since I'm not towing anything to make sure it's not that.

I'm at my wits end over this, any advice?