I think it's really up to the moderators of each forum (which is just me at the moment) to control what is sticky and what is not, and how long they are stickied. I'm pretty much planning on keeping the latest release notes stickied on the top of the chainBB forum, and I might leave the sticky post in General Discussion for a long time.
I'm not sure how a trending stickied page would work, unless stickies themselves were dynamic based on some sort of criteria.
That's cool and completely understandable, considering it's right in line with how stickies work in pretty much every forum (well, every forum I've ever used). I really like the idea of having this applied to Steemit/ ChainBB content.
For Steemit, I've been yearning for a "bookmarks" feature for each account. This would make it convenient for all Steemit users to save their favorite posts. As far as the "most stickied" post trending page goes, my idea is to have the content with the most favorites (bookmarks) for the last X days remain there for Y amount of time.
Even if the content remains on the page beyond the payout period, it still acts as an advertisement to the quality of work for the author that made it, not to mention it benefits the whole community to have the highest quality content remain visible the longest.
Social bookmarking could be an awesome feature for steem :)