If you store those MLs in a relatively dry / low humdity compartment and always-always make sure no moisture is present in the bore when you apply that (my opinion) crummy Bore Butter, then you increase storage time significantly using it long-term.
But don't ever believe those barrels won't eventually show pockets of rust. A good gun oil outlasts bore butter and even Hickock45 would probably tell ya' that his Ballistol storage treatments of his bores will outlast that Buttery stuff.
If I were you, I would discontinue it's use and switch to a good gun oil. There are several really good oils out there. Google some of them. Just stay away from ones built with a plant base like Frog Lube, which reacts poorly where it's stored in inconsistent temps and varying humidity levels.
The Frog also hate the freezing weather conditions. It will harden actions and get gummy=gooey when brought into a warm home right afterwards.