While they may not be needed for awakening, they may still be better to exchange for Rainbow Crystals whenever that is brought over. If you are unaware, in DMM if you discharge a gold+rarity unit you get Rainbow Crystals (event units give negligible amounts) which can be exchanged in the trading post for strong units.

That said, it was a fairly recent development on DMM so it will likely be some time before it comes to Nutaku, and Gold units only grant 20 crystals while most of the units offered cost 1000.