Having been in academia for a bit, I find it somewhat hard to believe multiple professional mathematicians in different fields give meaningful reply to a random email solicitation from an internet stranger within three weeks, simply because those people's inboxes are absolutely bombarded every minute.
In reality people would be thrilled to have such response even with a finished preprint on arXiv. Anyway if you really hit the jackpot hope it will be smooth working out the details and get it published!
Well, I was emailing specific people who were working on very closely related things, and had recently published papers about it and I had very small, concrete questions about their results and not much about my question, except for context.