From my experience, and from what I have seen from my research two weeks is definitely a minimum, but a month or so is much better. That gives them time to check out the product, plan a promotion, come up with bonuses, plan their mailings, etc.
As an affiliate myself, I only promote one product maximum per month to each list, sometimes less. I like to provide valuable content most of the time, and once in a while I send out a promotional email. I like to hear about products in advance so I can decide which one is most targeted to my list and send out a mailing about it. I want to make sure my list is getting what they signed up for, not just random offers that make me a lot of money. If I don't know about the product until a week before it launches, then I usually have either decided to offer a free report or I already have another product lined up, so the one that I knew about in advance gets the mailing.
Also, one month gives you time to make sure you have provided your JV partners with everything they need to promote your product. Some need custom landing pages, some want to do interviews, teleseminars or webinars with you, some will have questions about the product, etc. so it is good to give them a month to figure all that out, and then you have have time to help all of your JV partners sort out any problems they may have.
I have never launched my own product, but I have watched a bunch of product launches, and I have been a part of some, so this is speaking from my experience as an affiliate/JV partner. Perhaps someone who has actually done a launch of their own product will have something to add to this?
Shawn