I'd like to add that I did have PTL with #2 - I went into labor at 28 weeks and with meds and bedrest carried him to 37 weeks. And still carried my 4th baby to 40 weeks 4 days while nursing #3 the duration
I went on to tandem nurse for 27 months
I do think it is true that you get more cramping/contractions with subsequent pregnancies but that is regarless whether you are nursing or not. I get contractions daily now pregnant with #5 and I'm no longer nursing.
Keri