I've had my male and female ball python living together all year as they're both several years old, up to a good weight (2000g and 1200g) and I was planning on breeding them together eventually anyway.
However...I wasn't expecting anything this early in the year. Everyone I've talked to or article I've read has starting attempting matings in November and December. But last night when I went to feed everybody refused food (the first time my female wouldn't eat ever) and she was super aggressive - to the point where she was hissing and striking at me. I gave up and left her alone, and when I woke up this morning they were very clearly locked together. I can see through the side of the tank, and they've been in this position for 12 hours now. Both are proven, so they've done this before...but isn't it too early?