Another battery question

[Jeff_DML]

Replaced the original battery in our 4runner with an Costco interstate battery a year and half ago. I went to drive it yesterday and the battery was dead so I had to jump it. I did not leave any lights on as far as I can tell.

I work from home so I dont drive a lot and when I do usually pretty short drives. We did just recently drive it to go camping which was 2.5 hours each way so figure that should of charged it up.

Costco warranty is 3 years so going to call them on the warranty procedure. Question is are the sometimes bad batteries or should I look into my alternator? I am guessing Costco does not have the ability to check it. I might upgrade to the AGM if they have in stock, previously they did not.

TIA
Jeff