John;

Congrats on obtaining a pair of Spotted Pythons.

In regard to breeding, while size is an important factor, age is equally important. Female pythons should be at least 3 years old to breed. They may produce at a younger age, however the result often tends to be smaller clutches and infertile eggs.
Males however can breed at 18-months.

Also, you should not assume your Spotteds "seem to prefer room temperatures" because they do not use your heat spot regularly.
Most likely, your hot spot may be too hot.
Hit it with a temp gun and let us know the results.

Hope this helps!

Gary