I started off using the soft copper chrome supplies, hated it and they are hard to remove as much as they are hard to install at times, especially when you have a really strange offset leading to a toilet. Out of all that I've seen and removed........? They all show signs of leaking at some time given the greenish corrosion at the 3/8" nut, you can tell the difference between a leak and condensation dripping back.
I've seen many of the hard ones indirectly supporting a fixture like a wall hung sink or a toilet.
I use Fluidmaster or Watts stainless steel flex supplies only, ONLY with the brass barb inserts that connect to the crimps that hold the supply lines on.
Verdeboy on those that you are using,
If those have plastic barbs holding the nuts on, they break over time and that vinyl braided plastic gets hard a freaking rock. I've replaced a few of those for splits either on toilet supplies, faucets, then leading down to washing machine hoses.
I bought them because they was cheaper but I got away from the liability.
Watts has the tightest mesh pattern of stainless steel webbing around the vinyl tubing; Fluidmaster is wider which I don't appreciate but I appreciate the quality they use on the connections and the brass barbs for the crimps.
Stainless braided isn't foolproof, but it makes for a more less time consuming task. They do make a corrugated stainless tubing but isn't popular amoung plumbers yet.
I really wish someone would come out with a 7/8" chrome brass nut for toilet supplies in flexible stainless; I don't trust plastic and those nuts break all the time on stock supplied nuts that require your own hard supply line.