I guess my story is not a whole lot different than other men in my age group.
I have never had the pleasure of more than one shot. In fact, sometimes, I just can't shoot esp when I have had sex or masturbated within past day or two. I am a late bloomer, when it comes to this hobby. For decades, I had never been with anyone else except my wife. So, while with an sp, as soon as condom came on, junior stopped feeling anything. So, multiple shots during one hour session are out of question for me. Having said that, I have no issues with multiple shots with some gap between. Once, I saw two ladies within about 5 hours and having the second round was not a problem at all.
I have been planning to have a two hour session with one of my ATF. The plan is take a break, have a shower and try it again. May be I will be lucky to have my maiden MSOG session!! I have an alternate plan as well, which is to have back to back two sessions, but with different SP's but at the same incall. I think being with a new and fresh sp would certainly give my libido an instant boost. So far these are just plans so we will see when and IF it happens.
Everyone is different but I think a lot of it has to do with age. But I think if I had gotten used to condoms at an earlier age, things would be different. Having said that, I don't really have any complaints.