Since nobody replied I thought I would give it a shot. I have always kept my younger dumerils separated year round until they reach breeding age. At breeding age (around 4 years) I keep them separate until just before breeding season, then I keep them paired until I am sure the females are gravid. I feel my dumerils feed better, are able to take better advantage of heat gradients, and are less stressed when housed separately. I only keep them together when wanting a pair to breed. I keep my pairs together from early november until I see signs that a female may be gravid. I keep them together for quite a while because I have had dumerils breed pretty late in the season. That said I know of one successful breeder who kept his dumerils together from the time he got the pair at three years old until when he sold them at 12 years. His pair bred every season and had healthy litters. In short I would recommend keeping them separate, but if they both have separate hides on each end of the heat gradient, are fed separately, and feed well then in a 50 gallon aquarium its probably okay. Let me know if you have any questions.
thanks,
Erin