I clean my barrels every time I shoot it, if I have not lost my napier pull through kit that is!
But generally both my ev2 barrels like to be clean so I don't leave them go past 150 pellets.
You will have to find the best Die & batch for your barrel. Group at 45 and 55 yards to see which pellets group tightest.
Got about 12 different dies of jsb, pop to tondu one Saturday if you want to try /test some?
I don't clean the out side of my ev2, I just paint it black!