The longer the stud hangs out under the rocker arm the more sideways motion that the pushrod does. So you lose some effective lift with a longer adjuster. Also, the force on the adjuster goes way up since there is a longer lever arm trying to break it off in the rocker arm. Depending on the rocker arm design, the oiling can also suffer. Some rocker arms use a little piddle hole right at the adjuster to spray oil into the cup. If the cup isn't in the right location then the oil can't spray in.