Here’s the pertinent part of the reply I sent Dave to his question.
“I use endless-loop strings, made with low-stretch materials (never B50; changed from it to Kevlar in the mid 70’s), and don’t have any problem with string stretch (after the initial stretch), so my brace height stays where I set it [which is precisely why they use endless loop strings on compounds ]. I, too, leave my bows strung for long periods of time, only unstringing when I’ll not be using that bow for a good while, or when traveling. I’ve never encountered a tuning problem due to string stretch.
… because of the greater inherent flight stability as FOC increases, you SHOULD have LESS change in arrow flight with an EFOC/UEFOC arrow than with a normal FOC arrow, as brace height changes. …
I never liked Flemish splice strings because of the string-stretch problems I encountered, especially with the high draw weight bows, so quit using them almost 40 years ago!”