my target rifle gets cleaned one a year, usually after 7-8000 rounds of Eley Tenex. keep the bolt and action clean and free from crud, which is usually a mix of bees wax or tallow lube. some American ammo uses dry mica as a lube which is less messy.
the test barrels at Eley are not usually cleaned at all they just wipe the bolt face and muzzle and carry on.
the old priming compound contained powdered glass and some corrosive elements which needed to be cleaned out but that's no longer an issue as most of it is made by the Eley prime process and primer composition.