Stainless braided brake lines make the pedal firmer, by reducing flex and ballooning. Some people may not like the feel - the pedal hardly moves as you push harder on it. It can be tricky to modulate the brakes if you're used to the normal flex. But I like the firmer feel.
They do have to be checked more frequently than standard rubber brake hoses.
If you switch to stainless, do the whole car at once. I got cheap and only did the fronts at first. I wound up with rear brakes that came on slowly and let go slowly. I don't recommend it!
If your question is how often you should flush your brake lines the answer is in the owners manual. I would however suggest that if you reside in a very humid area to do it more frequently. Brake fluid attracts water. The water will vaporize when heated an will reduce performance and at worst could result in severe fading (a temporary no brake condition). Brake fluid contminated with water can also corrode brake part internals quickly. Using a quality fluid (not a racing fluid...they even attract more moisture!) is the first step. I used Castrol LMA (stands for low moisture absorbtion) on a prorally car with very good results. I did not have to completely flush my system after every event like my buddies who used racing fluids did. I never experienced fading with this fluid even under some pretty harsh use and conditions. Ford heavy duty truck fluid is remarkably good. It has a high boiling point, has low water absorbtion characteristics and is cheap.
probably bc the ford heavy duty stuff is DOT5 (i'm guessing here). just one more not regarding brake fluid, DON'T USE AN OPENED CONTAINER! for example, you buy the really big container to top off now because you figure you could use some later. WRONG! after it's been sitting on your shelf without the little seal on it, it will get moisture in it! throw it out and get new fluid.
if you were to cover the opening with some saran wrap or something and then put the lid on... i guess. but how much is a bottle of brake fluid. $2 or $3 for some dot3, right? just be safe and throw it out IMO
You can use racing brake fluid on the street IF you change it frequently. Most racing brake fluid will have a very high dry boiling point, but a mediocre wet boiling point - and the wet BP is the one that matters when the fluid gets old.
If you run track events where the brakes will see a lot of use (i.e. running laps on road courses for 20 minutes at a time), flush and fill the brake system with fluid from brand new, factory sealed cans just before the event. This is the only way you can be sure of having good dry fluid in the system. A long brake pedal is no fun when you're approaching a hairpin turn at triple-digit speeds. It would be a good idea to flush it again when you get back home - or even before you leave the track.
No matter which fluid you use, or how hard you drive, it's probably a good idea to flush the brake fluid at least as often as you change pads.
Oh BTW the Ford Heavy Duty stuff is DOT 3. And it's a good performer for the price.
Generally speaking, you don't want to use DOT 5 fluids in anything that gets driven. DOT 5 is silicone and not chemically compatible with DOT 3 or DOT4. DOT 3 is glycol based; DOT 4 is borate ester based. They are generally compatible with each other, but not with DOT 5. You have to do an alcohol flush to switch from DOT 3/4 to DOT 5 or vice versa.
Recently a new category was added, DOT 5.1. DOT 5.1 is borate ester based and in many respects is similar to DOT 4. I don't know much more about it, but the DOT 5.1 category name is confusing as hell.
DOT 3, 4, and 5.1 fluids are clear or amber in color when new. It turns brown (like bad coffee) with age and heat. DOT 5 (silicone) is purple. The color difference should give you a clue that you're not filling the system with the stuff that's already in it.
I must say, I'm impressed, we really have some people on here that know their brakes. I actually have nothing to add. I use the 5.1 in my bikes, seems to be good stuff, I change it once a year or so on the street. I figure in non-racing situations once every two years is okay. Basically if it starts to discolor to " bad coffee", as above, change it or sooner. Just for one more opinion, I have stainless lines on everything except a few antigues.