I don't know exactly but something along the lines of "using too much lemon oil on a fretboard". I remember someone saying not to wait too long before wiping it out.
My gut feeling is the gunstock oil/wax treatment is probably 100% safe, just wanted to confirm with long-time users.
I've treated my Silhouette Special neck at least twice a year since getting it new around 4 years ago. Sometimes more depending on how dry the neck felt. No ill effects here.
I do it about once a year - wipe on the oil don't leave thinking "if I leave it for xx hours it'll really soak in". Tear off another piece of kitchen roll and wipe it off. Do the same with the wax and don't use too much wax otherwise it will not feel like a "brand new from the factory neck".
Use some of the EB Fretboard wipes - I just used some on my JP rebuild - but I think I went over the top on the fretboard wipes - feels a little bit oily at the moment - still nothing that can't be buffed off