I agree totally with Tony on not using DT on fingerboards, it isn't designed for that.
I have been messing around with a fingerboard oil but getting that sweet spot has proven difficult but I will nail it.
So, either Dingowax or Dr Ducks are my two go to products.
I have also been known to use the old CA glue to seal and harden fingerboards made from Rosewood, as far as Maple goes I recon if it is Canadian Rock Maple it probably doesn't need anything other than a wipe of oil.