I wouldn't and I would advise against it.
Come nighttime, your tame little leopard gecko has a personality switch that can make them more agressive than they are in the day time.
You can try, of course, but consider it experimental and report back here with your findings. If you keep them with no ill effects for 6 months, I'd consider that success. Keep a close monitor on them, make sure both are eating and drinking and pooping.
How big is the cage? I'd recommend at least 20-40 gallons PER animal, with lots of space for each to establish their own territory.
What sexes are you intending on keeping together?
You can try it just as long as you have constant observation, and don't be surprised if you find one of them mauled to death one morning.