I've over 1,500 Kodachrome 35-mm transparencies dating back to the late 1950s. I've tried a variety of scanners and although most gave good results the time factor involved in scanning and processing meant scanning all 1,500 individually was an almost impossibly long task, so I took the commercial route and had them scanned professionally.
It wasn't cheap, but it wasn't expensive either and I'm more than satisfied with the quality of the results. I had it done locally and when I checked on progress the lady at the processing lab doing the scanning said she thought she knew my family intimately as there are photos of my kids from babies to young teen-agers that she'd scanned in and recognised!
My recommendation is if you've more than a couple of boxes of transparencies and can afford it, get them scanned to DVD professionally.
Certainly my kids and grandchildren can see these slides now, which before they couldn't without setting up the projector and screen.