With rotation, I think leather soles should be able to last north of 5 years. I have pairs from 6-7 years ago that still do not require a resole. The thing is, it's really tough to quantify (for me at least), because I obviously wear some pairs more than others. It would also be dependent on the quality of the soles; I had to throw out 2 pairs of Ed Et Al because the soles just felt plain awful and I didn't think they'd stand the test of time.
That said, I used to wear my Alden 990 and 975 as beaters(from 2015 - 2018); sometimes they'd be worn on consecutive days for up to a week due to travel. While the double leather soles on both pairs are pretty well worn, I think they can last for another full year of abuse.
I've been wearing my doak Dovers at least 4 times a month since 2015 as well and I think those can last another 2-3 years, maybe.