IMHO, unless you live in a climate where wood is likely to dry out and crack, then simply keeping your instrument clean and adequately humidified is all you should need to do on an ongoing basis. It probably doesn't hurt to carefully and lightly oil a fretboard once every few years - after checking with the manufacturer of your instrument to see what they recommend, but beyond that I consider most instrument treatments and polishes to be money-spinning consumables with little real benefit.
The people I know who are experienced in building instruments tend not to take much notice of these products, so I take my guidance from them, as they know much more than I do. They tell me I don't need guitar polishes and oils.
The only exception I make is for FastFret which I use on mandolin, but only because it makes the metal strings last longer before corrosion sets in. I don't use it as a treatment on the wood.
So, personally, I'd use my money on something else.
Just MHO, and YMMV.
