I used both a 901 (auto) and a 510 to start with. The 901 battery lasted a bit longer than the stock 510. I would get about 2-3 hours out one by switching between the 510 and the 901. Of the 2 Atty's that came with my kit, both lasted about a month of lite duty.
With 2 battery's you can
vape while charging the other. They take longer to charge than the stock 510's. I would also reccommend to have at least 2 spare attys on hand. For fun, take a look at some LR 901 Atty's (AltSmoke & Vapor Kings seem to have good ones)
And, yes, I do tend to like 901 Attys

My SB and REO both like them too!
GB