I saw an old man (80+) shoot probably 15 <0.25" groups in a row at 50 yards with a Winchester M52 with a matching vintage Unertl scope. I asked him why he doesn't shoot in benchrest competition and he almost yelled at me... Something like,"I don't have time to be where someone else wants me to be, I do things on my own schedule!" Now that's "ALL DAY LONG" performance! Pretty cool. If only my centerfire rifles could be that good!
When I shoot 3 slow 5-shot groups in a row with a particular rifle at 100 yards and they are all sub-MOA I think I can comfortably say,"This is a sub-MOA rifle". That rarely happens, but it does happen with 2 or 3 of my rifles, on occasion. I have never used the phrase,"All day long" describing the accuracy of my guns. In fact, I always raise an eyebrow when I here that and think of the guy with a Mosin Nagant with a Walmart scope that is supposedly a 1/4"MOA shooter, "All day long".