Joe- I do not suggest any imminent danger but I still say "why not care to do it right?" What you "can do" isn't always the best course of action. Longer shells in short chambers can and most likely will raise pressures. Is that an insignificant <5% or a more concerning 10% on a max waterfowl load? I don't think either of us can say for sure in a specific speculated gun/ load combo.
Now to te original poster 60 rounds for a few years of waterfowl hunting? I wouldn't rush to get rid of the "dangerous loads." But 60 rounds as a gateway to not caring and shooting anything, just not how I would do it.