Unless Testors has re done their clear flat/gloss lacquer formula, it will yellow over time specially over white paint. I have been using Future for well over 20 years too and have NEVER had an issue using it. One of the last older builds I had being close to 30 years old was sealed in Future and was recently sold on Ebay. The US Navy high visibilty scheme including the white areas did not yellow and the paint looked like the first day I prayed it on. On the other hand, I had Testors clear gloss lacquer yellow only after about 5-7 years.
Some modelers have a bad experience with a product or hear of one and automatically condemm its use. I have a friend who used Alclad for the first time and had an awful experience with the black primer. We have heard horror stories about that because the first black primer badges were bad and some even sprayed really bad.
Now he refuses to use Alclad and even gave me a couple of the bottles he had. And as for me, I love how Alclad sprays and the metallic tone it puts down.
Tojo
I also use Flory but I use it over a Future gloss coat which makes it easy to wipe off once it's dry. I have noticed that if used over a flat coat, it makes it a lot harder to wipe off and will darken the finish a bit, acting like a filter.