I vote always, because it's always if I want to.
Sometimes I don't need or want to orgasm. I just enjoy the, uh, conjugation.
Sometimes it does take effort on my part to come, especially in positions other than missionary and on top, and sometimes they come slip-sliding along very quickly and with little to no conscious effort on my part. But it's something that I worked at...I went into this on the other thread. Don't have time to re-write it this morning...