On the off chance, have you looked at both poly and gut / poly on low tensions?
When you say durability, you're talking about the playability of the string rather than the string breaking correct?
I usually define it as the former being longevity and the latter being durability.
99S - GS SB 17 45 (Meh at first, then Love) / EP 2.0 - TB 19 30 (Powerful at first)
PT630 - PNG 17 62 (Backup) / POG 110 4S - BHBR 17 59 (OK)