Comedown?
I used to take GBL (converts to GHB - Gamma-Hydroxybutyric acid) 24/7, it is a downer and has no comedown. IT has withdrawal like any other gaba enacting subtance (barbs, benzos, booze, phenibut etc)
IT doesn't take long to get addicted to benzos. Long enacting benzos like valium have a huge half-life - anything from 20 to 100 hours. Use valium even sporadically and you will soon become dependent.
Xanax is the worst benzo for withdrawal because they hit so fucking quick