I am building a page that will include a single main post area that will show a featured picture and excerpt from a post and below that will show older posts with just their excerpts. I intend to devote enough space to the new/main post to allow it to be say 200 words long. However for the old posts I only want to devote enough space for say 100 words. Of course this will impact the way that I write my excerpts so that the first 100 words are a sufficient "hook".
I have seen some code that allows you to change the length of an excerpt generated from the content of the post but nobody seems to tackle the_excerpt. How I can I write some code that will retrieve the explicit excerpt (the_excerpt) and return only the first 100 words? Can I do it on a sentence level?