Sorry, I wasn't very clear in what I initially responded back with.The code that I use doesn't create a new sitemap but rather just adds an additional node to the current one whenever a new page is added, so yes I am using the type of sitemap code that you are referring to.
BUT, since the site grows at an exponential rate it means that for every one video uploaded it will be matched up with each and every other single video to create a unique URL for each combination.
As an example if there are 10,000 videos currently on site which means there are 2 sitemaps right now and ONE more video is uploaded that means that 10,000 NEW unique urls/pages will be created thus creating 2 additional sitemaps resulting in a total of 4 sitemaps because of one new video being uploaded.
Let me know if I need to clarify anything.