Change the latter one to "true" and keep an eye on the list shown when typing about:sync-log in the location bar.
Delete some of the files (in case this doesn't happen automatically—I did not check) once you'll have got too many of those.
Thanks again, co-rel
As you can see your answer was super-helpful.
P.S.: It's good to know this stuff, since I checked and had sync time from start to finish anywhere between 20 seconds and 4 minutes (and I am on fast high speed). It's really easy to shut down the computer too early. It's a good idea to always issue a manual Sync Now command when you know that you'll switch computers.