That's more or less what I did, and I'm glad I tried out a cheap folder more extensively than just taking one nice folder for a test ride. I bought a cheap folder at a pawn store for $50 and rode it everywhere I ride my other bikes. Then I found out other things which were great about folders in general, like taking it traveling or transporting it by bike to loan it to a friend while his bike was in the shop, etc.

During this several month-long tryout period I started figuring out which features were going to be the most important to me, like size when folded. By the time it was spring (when I had planned to buy a folder), I was very confident in my choice and I knew which bike was the best for me (and it was a Brompton).