Suburban dilemma

Before I took it to the mechanic, the battery was dead. I jumped it and it started and indicated it was charging. Next day, dead battery. I replaced it at that point as I had left the truck running the day before when I jumped it for an hour (trying to get it to die again which of course it didn’t) and the battery had charged and it would restart no problem. When I removed the battery, it wasn’t holding a charge, dropping one volt in an hour, which is why i replaced it. Previously, it had never killed the battery.
I am really at my wits end with this one.