For a 1000 gram and over ball python fasting for a month is no big deal. Some of my ball pythons have fasted for as long as six months, didn't even lose any weight hardly at all. I wouldn't sweat it, just keep offering weekly. If you are worried about wasted rats you can get another snake that will always eat, like a dwarf retic. That's what actually got me in to the dwarf retics LOL. If I change the ambient temp in my room I'll have a few ball pythons go into a fast, doesn't matter if it's hotter or colder. I'd say after 2-3 months of not eating you could offer a fresh killed adult mouse, or a small live rat, that usually does the trick.