DD is currently 18 months. Definitely would like to have another one but no more, was originally thinking a 2.5 or 3 year age gap would be good, but someone helpfully pointed out to me recently that I'm no spring chicken (37 this year) so should just get on with it! Had a rough time with DD in the early stages thanks to emergency section and resulting complications for us both, so likely to be an elective c section next time around with all the fun of recovery. 
Would love to hear other people's experiences/thoughts.