How much time to wait for answer after postdoc negotiations
It is not clear from your question what you are waiting for. Based on your description of the conversation, you should continue to look for post doc opportunities until you have a firm offer. Do not wait to hear anything more before sending out more applications. It is probably worth noting that 10 months prior to defending seems very early to be actively looking for a post doc.

If you are talking about how long you should wait before giving up hope, then you should wait as long as possible. Right now you do not have another offer, so there is no reason to move on. 

If you are talking about how long you should wait until contacting the PI again, I would say generally 1 or 2 weeks between attempts. You might be better off making a phone call next time.