IMO boiled linseed oil is pretty nice for a lot of uses, but I would not put it on my guitars. I have on several pieces of furniture etc. though.

Several reasons: 1st is linseed treated wood can develop mildew in a matter of hours or less under the right conditions. Walk home in a rain once and some moisture gets in the case, don't be surprised to find the neck full of greenish-black dots. 2nd it gives next to no protection from wear and tear - it may feel nice to the hand, but pretty soon you realize it also wears the wood when you play it, and also collects loose skin bits in the wood pores etc. so keep your hands extra clean when playing. 3rd you can pretty much forget about any other finish later on as most stuff just won't stick on oil-treated wood. 4th using too much oil can act much like water, saturating wood and causing wood fibres to extrude and perhaps also cause some looseness in frets etc. plus overall lessen the structural strength of dry wood. Also linseed oil is fiercely flammable and smells kinda weird to me.

There are better, more modern wax/oil treatment mediums available, which are often hailed as great, but if you want the guitar to last 20+ years and remain nice and all, I'd recommend a professional grade full laquer job which can be made satin too if you like satin.