I want to share what I have learned.
Metal is very porous. Lead film from slugs , or pellets will fill these in making a "seasoned barrel" more accurate , so as long as accuracy is there it's best not to remove the seasoning by cleaning. If accuracy changes then after a cleaning shooting a few dozen pellets , or slugs will re season the barrel. Slugs often cause more fouling due to higher contact with rifling , and higher velocities.
Competition shooters I have read seldom clean , but with a new barrel it's best to remove factory barrel coatings put there to prevent rust. Being as different manufacturer's use different alloys for the pellets, or slugs it's possible that if accuracy changes a lot then a cleaning may be necessary.
This can be frustrating trying to find the best pellet for a new barrel , so after testing different brands , and weights then finding one that shoots the best stick with that alloy for best results. OV