Yes, I'm sorry I wasn't clear - it is not required that you can only have the revolve axis at the end of the curve.

But if you do want to place it nearby the end of a curve, then you should make sure that you snap it directly on in that case, because you can create a bad surface if the generator curve is sticking out a little bit past the axis, like this:



And if it is very close by but just a little bit on the other side, then there can easily be a hole there that you might not see very easily since it could be very small.

- Michael