I submit only the quality posts.. no matter how many times.. but normally once or twice a week !! and it will be a SUPER QUALITY page !
i would suggest to read articles on how to best use social bookmarking sites to get the most out of them without giving the impression of scamming / submitting your own site too often. i also agree with tharshan's point
As many as you want, there really isn't much limit on how many times you can submit differnet pages of your website to social bookmarking websites, your probably better off just posting different pages of your website to the top 5/10 social bookmarking websites, many of the smaller social bookmarking websites with have low page rank and the "link juice" from their websites will be pretty worthless.
I only submit my site ONCE! But I often to bookmark many of the pages of my sites which are good as well.
Submit as many as you can but choose the high quality BM sites and make sure that your submission is quality too.
There is no fixed limit for this, you can submit as many as you want... But make sure you are not spamming these bookmarking sites. Since, social bookmarking gets you backlinks, so you have to be a little careful otherwise your backlinks may appear spammy to the search engines.
There is no limitation on that. But there is no worth in submitting your story in low quality bookmarking sites. So be sure to prefer quality rather that quantity.