I guess it is a matter of perspective to say one can use sheepsfoot too much. You could also say that you added too little water to maintain soil moisture and optimize your compaction efforts. I don't claim to be an expert but the technically correct use of a sheepsfoot really just means rolling until it "walks out" of the fill, if moisture is a problem, then you need to add it until you have achieved desired compaction, then add the next lift or begin final grading. I realize not always practical or cost effective to add water and not every job gets tested for compaction, especially a private pond job, but in my experience to say you can roll too much only applies to black top or pavement work, not dirt. If you are not allowing the sheeps foot to walk out of the fill, you cannot say you are consitantly getting compaction.
