years ago i had a mechanic friend make me up lines from hose and fittings, they were great ( except i forgot to get the clear hose to cover the amazingly abrasive braided bits ) they fitted exactly and improved the sh1t brakes on the vmax no end
however several months of trouble free operation later i was exiting a freeway at some speed over the limit, went to grab a handful of front brakes at the beginning of the turn and ...nothing - the fitting on one side had unscrewed at the caliper end of the line. brown trouser time. luckily the rear brake was enough to get me out of the situation but not fun. much slower rest of ride home
not saying anyone did a bad job, they had been great for months, but they obviously need checking regularly, which isn't something that normally gets done with pre-made lines