I think for normal maintenance-type use, about one ounce of Sea-Foam per gallon of gas is recommended. You _can_ run a bit more than that, but the use there would be for winterization or extended storage. I put my Shadow into hibernation, and I think I was running about 3 ounces of Sea-Foam for the 2.5 gallon tank.
I can't speak to any other fuel system cleaners, but too much of anything can't be too good. A little bit of cleaner over a long period of time is probably better than a blast of cleaner over a tank or two.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.