The "Lightning Deals" help page states that they will have a limited amount of each sale item, on sale for a limited amount of time. When they all go, or the time runs out, that's it. I expect that they'll release the deals on the hour in a similar fashion to the 24 hour sales we've seen before.
The bit that will be frustrating is the queuing system....
#6750499, By SmoothMartin Amazon UK Black Friday
SmoothMartin 870 posts
Seen 12 hours ago
Registered 14 years ago