All the time before I was married!
I had really self-involved partners and I had a terrible time having an orgasm (I'd try for 20 minutes, 30 minutes, sometimes even hours). I had to fake it for an ego boost- One partner actually got mad at me if I couldn't, like I didn't cum on purpose to make him feel less virile. I had another partner that didn't even care if I got off, he was only focused on getting his nut- squirrelly guy but his dick was HUGE, obviously I didn't stay with him because he was Prince Charming.
When I met my husband, the first 6 months of our relationship I faked it. He couldn't tell the difference- especially when I would squeeze my PC muscles to simulate an actual orgasm. I'd be overly vocal and just put on a show. THEN we got married and it all changed. I said- you know what? You never really focus on me and he said he felt like he didn't need to because I always got off. The lines of communication were opened and he made me promise never to fake it again.
Now if I know I'm not going to be able to (which is a rarity) I say, "I want you to cum for me" and I'll buck against him whenever he stops thrusting to keep himself from cumming. He sometimes asks why I don't want to cum but he'll see the look of frustration on my face and realize it's better to get it over with than try to hold out until I can. Then he'll have me lay back and he'll get me off with his hands and mouth. I LOVE having an orgasm when he's inside of me but some times it's just not going to happen.
The sex is better with my husband, I mean sure, it's less of a production, but he knows me and can read my facial expressions. HE ALWAYS knows when I'm going to cum, if I tried to fake it at this point he'd be able to spot the black sheep in a sea of white ones. What he and I share isn't just a sexual relationship anymore so faking isn't required- we share an emotional, spiritual connection and I'm not going to destroy or cheapen that with screams of "Ohhh, yea! I'm cumming", when in fact I'm actually not.