I checked out your url with the goal of trying to find items that could be excluded from the sitemap, such as images, search pages, duplicates, etc.
Fortunately (or unfortunately for sitemap generation), I could not find anything. I believe your site goes beyond the limits of my generators capacity.
I plan on releasing a new version today, but I doubt that it's going to do much more for you than what it's doing now as the changes are not deep indexing related.
I wish I could give you a number and say that the generator taps out at X amount (I wish I could say it never taps out : ), but how the site is designed (complexity) has everything to do with how many pages get spidered.
Wish I could offer more! BTW - you have a great site and I'm 100% confident you'll be doing well if you're not already
Best regards,
Jim.