I always have the GPS on unless it's a local bimble but I can't see why if you have the other gear on board that you shouldn't have it tuned in and set up. I usually have every bit of nav kit on the a/c switched on. Bit daft not to if you have it; plus there's still some satisfaction to be had from NDB navving. It's a bit like driving around using an Austin 7. Not very modern but satisfying in it's own way, like getting a sextant out on a yacht.
Disclaimer: I will however praise the Lord when they finally get shut of NDB approaches.