I take my SS-31 daily with my Xulin 3.
I use pens for peptides I research with daily or at least multiple times a week. That's where the efficiency really helps.
You are taking a much high dose than I am, so I can't attest to the stinging. I'm using 4mg/day in preparation for a MOTS-C cycle. I might bump it up to 6mg/daily.
I felt like the doses in the 20-40mg range were more aligned to the study for Barth Syndrome for major mitochondrial disfunction. My goals are more athletic recovery, performance, and healthy aging.
Good luck!