It´s negligible depending on how much the engine has been beat on. I was lucky on my Magna that it was relatively well taken care of. I have encountered no real cam problems on the bike since I´ve purchased it and with this in mind I plan on just waiting until she needs a good tune up to look into the cams.
A simple remedy of enlarging the holes is what I plan to do once the case needs to be cracked for an overhaul and inspection (if indeed it needs it).