I own 4 6v 8Nís and 2 6v 1929 Fords. All now have the same battery, a Deka, model 901MF (made by East Penn) or the Duracell equivalent, Ultra BC1.
I always run the vehicles to operating temp every 3 or 4 weeks if they haven't been used. To make sure the battery doesn't discharge, all now have hard wired Battery Tender float chargers. (And that will extend the life of any battery because it stops them from discharging.)
On average, I get 8 years out of a battery. I had one battery that I replaced in September, 2020 that was 12 years old.