I agree that mono and fluorocarbon need to be changed out quite often. In years that I fish a lot of tournaments, I might not even keep my mono a full year. As far as braid - mono backing is a great idea and keeps costs down. I spool up 2/3 or so with KastKing mono (which I use for my mono set ups and I've never had a problem with it). But then, on my bait casters, I never go smaller than 50 pound, and I usually spool 65. I use Fortis, too, which I think is a really good line, and not very pricey - I switched from PowerPro and I don't see a noticeable difference (other than price). The reason I don't go any smaller on my bait cast set-ups is it cuts down on the line cutting into itself on the spool. With 15-lb., if you get snagged on something and try to jerk it free, the line diameter is so small that it will cut into itself.
For my spinning set-ups, I use braid with no backing. I tie the braid right to the spool and secure it with a little piece of electrical tape. The tape stops any slipping that might be happening. I use 15-pound on the spinning reels because they don't lend themselves to the line cutting into itself due to the way it comes off the spool.
I keep my braid for two years, but on my reels that I use heavily I will wind it off one reel onto another so it's "backwards" on the new reel, if that makes sense. I think that is what you were saying you were doing with some of yours, anyway.
When I use a fluoro leader, I use FluoroKote, which is also a KastKing product. I am not a huge fan of fluoro as far as spooling just that on a reel, but I do use it for leader material. They also have a regular fluorocarbon now, rather being coated with fluoro - I haven't had a chance to use it yet, but I would imagine it is as good a product as the rest.