Found this while looking for something else, thought some people may find it useful.
This is a great article. I'm so glad you took the time to post the link. Thanks for letting us see it because it's just what I needed, as I have a little grapevine in a container. It got one lone little bunch of grapes on it this year. Last year when I got it it came with five little clusters of grapes. I don't think I should have left them on the vine, but the lady at the nursery said it was okay.
I don't know how long it will live because I live in Louisiana and it's a Concord grape and I've been told it WILL get a fatal disease. :( Didn't know that when I got it. I got it because of all the vines they had at the nursery, this one seemed the strongest and had the most grapes on it in spite of the high heat. Live and learn, but I'll take good care of it for as long as it lives.