I'm too tired to write a whole technical post on this, but here's the short version:
There are three types of brake flex hoses - OEM grocery getter, OEM performance and stainless aftermarket.
The OEM GG ones are long-lasting but not particularly good at preventing expansion under pressure.
The OEM perf lines are excellent. OEM 2012+ Boss 302, 2013/14 GT500, GT350, 2020+ GT500 lines have about the same expansion characteristics as stainless steel lines. It's a special product from Goodyear (as I recall) and there's no reason to change them. If you look at how Ford has terminated them at calipers there's a long length of steel tubing. That protects them from heat, and more important, it protects them from twisting.
Aftermarket stainless lines. It's a total crapshoot. Teflon-lined stainless tubing doesn't handle end-to-end twist well at all. If these lines are twisted end-to-end, they'll fail fairly quickly. Some products, like Goodridge for the S550, follow the Ford OEM architecture and layout - the Ford engineers designed the OEM brake flex lines with zero twist and the Goodridge lines are made with the same shape and they don't twist either. I can explain how it works but I won't do it now. Suffice it to say that if the S550 replacement line doesn't have a length of rigid pipe at the caliper that puts the flex line termination up by the side of the strut then the the lines have a limited lifespan in the vehicle.
Update: Okay, so not so tired now... The bit I left out is that the OEM lines on the FP S550's are either too short or the wrong shape for most aftermarket calipers. That means you're kinda stuck with aftermarket brake lines if you install someone else's calipers. Most of the "DOT" stainless brake lines that come with a kit have a plastic jacket (keeps dirt out so the teflon doesn't wear and fail) and the ends are properly strain relieved, etc. Thing is, unless they more or less follow the OEM pathway from the caliper to the hard line, they'll twist and that'll wear them fast. Here's the front axle pathway in the GT350:
Notice how, from left to right, the rubber line starts by going up, then turns down, and then up again where it terminates on the hardline fitting. If you're curious why this matters, here's how to demonstrate the effect. Take a piece of hose or a short USB cord, form it into that shape and then rotate one end relative to the other, the way the brake line in the picture would rotate with steering inputs. You'll see that the up and down curves bend and change shape, but the hose itself doesn't actually undergo any twisting from one end to the other. That big mounting boss on the caliper and the length of steel tubing make sure that the end of the flex section is exactly where it has to be to ensure long life and minimum stress. A stainless flex line that's flex all the way down to the caliper boss won't be able to hold that shape and it will experience some twisting as a result.
So, that's the rest of the post.