Hi,
This is a tropical plant that blooms so late so it is tough to get ripe seed from up north. I would keep a close eye on the pods to hopefully see changes, like dryness or color, indicating the seeds are about ripe. If you don't see any before frost is coming, you'll have to cover the plant for the night. Sometimes around here, we get an early frost, but then the temps stay relatively nice for awhile, so that could happen for you, and with covering the plant, you'll stretch out the time needed for ripe seeds.
Remy

How long does it take them to ripen because I'm having the same fear even though I live in SC and might not get a frost till Nov or Dec.

My vine has had pods for about a month or so. Only a few have ripened. I have managed to get some seeds and hope my other pods will ripen before the frost. It takes a LONG time. If yours don't ripen in time, I should have some extra seed to share. Nikki

My seed pods seem like they have been there for well over a month too. I noticed last night that the stem had a little brown on it but not sure that they will be ready before the frost which looks like a good chance next week. I am going to try covering them. They are still loaded with blooms. Keep your fingers crossed. I'll be happy with a few for next year. Kathy

Are we talking about the one that has the big leaves? My pods have been purple for almost two months but none of them are changing color. What do the pods look like when they are ripe?