Personally, I'd take the plunge, because if you don't IMO you'll probably wish you had and the longer you wait the more content you'll be moving. I have one that's done and has extensions and I WISH I had removed them the last time I made any changes to the URLs, but didn't and probably won't. They'll stay that way, because it's too big a hit on traffic for me to change them, but if the site was going to grow significantly rather than being updated at the site it is, I would probably remove them from that one too.
Anyway, my .05 (inflation) is: Remove them and be done with it or you'll probably look back and wish you had.
Note: On a site the size of yours the redirects should 'kickin' quickly in my experience (2 to 7 days), but the site I'd like to remove them from is significantly bigger, so it takes longer for anything to work all the way through the system. If I knew it would be 2 days I'd just do it over a weekend, but my best guess is a week to ten days and that's just plain too long when it's not really necessary to remove them.
Msg#: 4110818 posted 6:51 am on Apr 7, 2010 (gmt 0)
I would do it. (just recently did on a very large website)
Projections and experience put the re-index within a 4-5 week time-frame for us and we actually seem to be outperforming that projection. Current estimated re-index is about 3 weeks total. The website is a lot larger than yours though. I agree with MadScientist - you should be done in 2-7 days, however it depends on your backlinks. We redid and optimized our internal link structure at the same time, which is why we are being crawled better. Some parts of the website with a weaker backlink structure are taking a longer time to be re-indexed than the better linked areas.
Also, if you can, try and get "old" external links with the .html extension changed if you have any influence - and build some new links to the new URLs, that should go a long way in helping keep your rankings.
Msg#: 4110818 posted 6:59 am on Apr 8, 2010 (gmt 0)
You'll get dinged on the internal link values when you drop all existing URI's if you don't have the proper redirects in place immediately. The new URI's might also have trouble with getting indexed because they'd be considered duplicate when the content moves to them.
Save yourself a major headache and get your redirect system in order first. If the CMS is wordpress there is an excellent plugin called redirection by John Godley that I've used several times with excellent results. Google it.