I have always used products like Son-Of-A-Gun or Armorall on mine to both keep them clean and protect them.
Since it first came out - Armorall was the best, but it's been shadowed by Son-Of-A-Gun since it has a better formula I feel and isn't sticky like Armorall.
Things like the chlorinated hydrocarbons or synthesized organic oils are going to dull the finish. These are products like 409 or Fantastik. Just be careful what you decide upon to actually clean a cab.
Once dulled, it's hard to bring back the newness of the OE shine.
Even my 1960s cabs and amps look better than the day they were new.
Here's my 1996 Crate half stack

It looks nice and still shines. I've had no Tolex deterioration in all the time I've owned it. In fact it looks better than new I think.
And here's a year unspecified (prolly early 80s I think, maybe older) Peavey PA amp I own :::
I didn't put those stupid screws through the aluminum rails either! That's my next project to get new rails.