It is my opinion that you can house two snakes together if done properly. My first snake I had for over 20 years, 10 of which she shared a cage with my boyfriends snake (he took the snake when I booted him out). Both snakes were very good eaters, they shed well and showed no signs of stress that everyone talks about. Neither snake was ever sick so I never had twice the vet bills, but IMO a sick snake would be a sign that you aren't caring for your snake properly. Of course there is more work involved in keeping two snakes together but if you are dedicated it can be done. They of course have to have separate hides, in hot and cold zones, they have to be fed separately, and you have to keep a close eye out, just in case they do need to be separated (I have a separate 20 gallon that I keep on hand "just in case"
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With that being said, if you intend on breeding them, don't bother putting them together now, keep them separate. And I may be wrong, but I don't think you need to worry about dropping the temps until you are ready to breed, but that's a question for someone with experience breeding.
I hope this helps.
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Tosha 
1.1.0 Ball Python (Harry and Fluffy)
0.1.0 Siberian Husky (Kita)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Dessert Tortoise (Pope)
5.4.2 Fish (1,2,3,4...)
0.0.1 Frog rescued from pool skimmer
0.0.2 Lizards rescued from pool skimmer