Never follow the example of a pet store. Their focus is presentation so people can see the snakes and want to buy them. They also house them together because they simply can not house them all separate in most cases.

While it can be done it makes things very difficult especially when they are not of the same sex.

Some issues can be if one gets sick it can get the other sick.
Its hard to tell which did what as in loose feces, regurgitating, refused feeder.
You need a large cage with several hides and several heat sources so they are not competing over one.

Then the main issue is they are not going to wait on when your ready for them to breed. When they think their ready they are gonna start without you. This is especially hard on the male as they will exhaust themselves even to death performing the mating process. Breeding takes a toll on both sides and if you are not prepared to breed they should really be separated, IMHO.