Have a look at
www.tucows.com and search for jpg reduce batch
There are a few programs which claim to do it. Most of the stuff on that site is "shareware" so may have limited functionality (but there are ways around that sometimes!). Often with this kind of product it will be that you can't "save", rather than an expiry, which is a bummer.
If you find a product but need some kind of activation for it, drop me a note with the product name and version (unless you already know the places to go, he said mysteriously...)