I won't deny that it upsets me for irrational reasons if my fella doesn't finish.
+1
One of my LTR's didn't disclose that he was on antidepressants that affected his ability to finish. I internalized his inability to orgasm as I was doing something wrong/he was attracted to me/he wasn't over his ex/etc. and it fucked with my self esteem. Once he disclosed it, then I went down the rabbit hole of "what else isn't he disclosing", etc. Not a happy place and it contributed to the demise of our relationship.
Ironically, my current guy is on same meds and disclosed it right away. Fortunately, he wants me to have a good experience and can stay hard for-EV-er so I can have as much fun as I want to have. When I've been satisfied and he hasn't had an orgasm yet, I'll sometimes ask if he's got one in him or not... if he does, we keep going. If not, I tell him that I'm happy.
OP- can you offer any insight on how you'd prefer for your partner to verbally "tap out" (and she's just hanging in in hopes of you getting yours)? Also- if you feel comfortable with sharing, do you know why you don't reach orgasm (meds, physical condition, etc)? Asking in case there might be a difference in approach.
Also- I'd offer that it has been HUGE for me that the current guy told me upfront. If there's a physical/medical reason for your inability that you feel comfortable sharing with your FWBs, say so. And if you have a preferred way that they "tap out", offer that to them. That'd go a long way for me not feeling obligated to keep trying, if I were in their shoes. Or no shoes, as the case may be.