My precision rifle barrel logs show an average of 225 rounds between cleanings overall. I clean the chamber, bolt lug recess, and bolt raceways every chance I get.
All of these barrels shoot .25-.50 MOA. Clean or fouled, they shoot equally as well and to the same point of aim. The only difference has been in velocity. One 338 barrel would run 35-40 fps slower with a cold, clean barrel. After 4-5 shots, it would stabilize and run at normal velocity. It was repeatable, but I always foul my barrels with at least 5 shots before hunting with them.
I did have a Sendero with a factory 300RUM tube that would drop off from .75 moa to over 1.5 after 100 rounds or so. Clean it up and it would shoot for another 100 rounds! It has been my experience that a good, hand lapped barrel requires much less cleaning than mass produced factory barrels...if you're worried about it. I used to clean my "normal" rifles after every time out, because I thought I had to. The barrel in my Ruger 338WM is so rough though, the copper fouling never comes out. That rifle will still shoot sub-moa consistently, but I never put as many rounds downrange with any of them like I do with the long range rigs.
I think everybody should collect as much "data" on their rifles as possible. The key to a long range cold bore hit is knowing what your rifle will do under all conditions. If it shoots differently clean or fouled, it has to accounted for.
My rifles aren't stored for very long between shooting sessions, so they stay dirty in the safe. If I get bored, I might pull one and give it a good cleaning, but I only do it if I can step out back and confirm zero or something to foul the barrel.