I don't know if it's applicable to drum/tambourine heads, but when the kid was in little league (~25 years ago) about the only instruction he got from the leadership was that neatsfoot oil should never be used on a baseball glove, because it encourages the leather to stretch and become "flabby."

In that case, a special "glove oil" was recommended, that was sold in the US under a trade name something like "Glovolium" (?).

Other "leather treatments" like "saddle soap" also were deprecated, for the same reason.

Maybe someone with a skinhead that's been a problem has tried something like this - or would like to - so they could tell us all whether it actually works any differently.

I can't really offer much of an evaluation, since I think the kid hocked his glove to buy a couple of drumsticks for his trap set before the glove had time to "age properly."

John