I've been seeing HeroAca as a story in three acts for a while now. Without spoiling anything, Act One lasts from Chapter 1 to Chapter 95 or 97, and Act Two lasted from Chapter 98 till now. So I'll assume Act Three, which began either this week or next week, will last somewhere in the middle.
So I'll say MHA has about three years. Would be real cool to end it on the series's 10th anniversary in 2024. I'm more confident that HeroAca will have finished running in the magazine by thre end of 2025.
...my goodness, One Piece might actually outlive HeroAca.
Hell, let's expand things - the way I see it, I don't think Dr. Stone, Jujutsu Kaisen, HeroAca or Black Clover will live to see the end of 2025. One Piece might, but I'm still uncertain. That's still 3 years out, for sure, but things are definitely going to be changing again soon like they have in 2016 and 2020. I hope the magazine will be ready by then.