Cleaning between groups, depends a lot on the barrel. Some barrels foul more than others.
When I'm working up load data, I'll clean between groups but fire a fouling shot before starting my next group.
When I'm done shooting for the day I'll clean the bore, and fire a fouling shot before taking the rifle home to put away. I won't put a bolt gun away with a freshly cleaned and oiled bore, unless I've been shooting corrosive ammo, or the rifle is going in to long term storage mode (then it gets a full coating of heavier oil, in and out).
This is a personal preference thing. I prefer knowing my rifles are ready to fire the first shot on a cold bore, and have precision.
AFTER I've worked up a good working load, I clean as often as the rifle needs it. On most, that's 60-80 rounds, any more than that and I've got a copper mess on my hands that becomes much harder to deal with.
SOME of my rifles which are long on lifespan, need cleaned much more frequently or they'll start collecting copper fast. My old 300 Win Mag barrel, for instance, would turn a patch soaked in Sweet's solid blue, after just 3 shots. The throat erosion was bad enough by the end of it's life that it would foul up with copper really fast. The new replacement barrel, takes over 50 shots before I get any traces of blue on a Sweets patch.