Question about multiple shots?

So lately and I'm not really even sure why I've been able to stay rock hard after I finish. To the point where I can keep going even after I crossed the finish line.

My question is should I tell the companion I finished or is it OK to keep going for a second one.

Ive had it happen the last two times with two different woman. I finish but remain hard as can be. I kept going for a minute or two realized I was going to stay hard. Then let them know I was done.

So is it OK to keep going or should I let the girl know.