With the old adage "If it ain't broke,don't fix it" in mind......If the load in question is accurate,safe w/reasonable pressure and effective for whatever use it's being put to,there's no reason to change.

A great many powders will "work" in 30/06 class cartridges but as others have said,3031 would not usually be considered optimum.I've always had the best results with 4350 with the 30/06.There are other powders which do quite well with it but most of them are actually not far apart from 4350 in terms of bulk/burning rate.