Providing that you're the one who's thrusting away, do you keep on:
A. Thrusting away until the eruption stops or you're completely worn out.
B. Stop and just erupt inside her.
C. Pull out immediately.

And if it's the girl working the hips:
A. Let her keep going until she stops on her own.
B. Tell her you erupted.

Just asking out of curiosity.