I have great difficulty in achieving orgasm. As a 51 year old, diabetic, male on psych meds that is not really a surprise.

I still find sex very enjoyable. You are right there isn't a clear end signal. If you and your partner can talk about it openly, especially before it becomes an awkward issue between you that will help. I think you can come to a mutual agreement as to when you are ready to stop and transition to after play, cuddling, or just getting dressed.

Open communication is a wonderful component of a good sex life.