The only thing i notice was that if you engine has high wear on parts and the old oil sludge is probably doing some good by acting like a barrier. Such as on worn rings or gaskets, if you clean it you lose that barrier and may end up having more problems.
Dave when we cracked open my old 200,000 mile motor I was surprised at the lack of sludge..there was dirt/oil residue, but not much at all. I was even more surprised at how easily carbon could be removed even by just a finger nail..I woundered just how often carbon deposits had worked loose and been jumbled around in the cylinders before making it's way out the exhaust port. I would be more less concearned about attempting to remove any deposits via seafoam (assuming it does work..which people are indicating it does), than allow the buildup to continue. Carbon build up seems like it would have a fairly abbrasive quality on the internals of an engine..of coarse this is all just opinion based on my observations with my high mile motor.
Not a great pic for seeing the build up on the pistons..but gives you maybe some idea of the deposits that are already present and better left gone IMO.