Michael, I would venture to say that you speed things up, because you aren't really *rebuilding* your file, so much as recording your transactions. For instance, if you read my article https://microsoftmoneyoffline.wordpress.com/2019/12/10/discussion-eliminating-price-data-to-reduce-file-size/
, you'll see "I’m happy to report that by deleting the prices for 3 more stocks that I’ve owned for quite a while, I’ve reduced my file size down to 56,226 KB, which is now 10 MB smaller than 1 week ago!!".
Price data and quotes for investments takes up a lot of memory, and slows things down. Every time you do a stock split, spin-off, etc., every single historical transaction is repeated to reflect the new shares and prices. If you were only using your program as a checkbook register, rebuilding your file would probably be a repeat of the old file, minus all of the custom reports, recurring bills, etc., but I'll bet you have investments too, and you are losing all of your basis history when you start over and just record your portfolio positions.