Thank you for the info! Your link, Gardyloo, is for the Visit North America ticket only, correct? Even though I don't know much about fare classes (I'm happy that by now I recognise Y, J and F when somebody uses that), a look at the prices tells me that indeed booking seperate flights would be (much) cheaper, so S and V seem to be rather highly priced Economy tickets. I guess it really only pays off if you need to be really flexible on short notice, which I don't.
jacknyoc, I'll make a note of the Jet Blue month of travel, but indeed it seems to happen in September whenever it happens (and information on it that is not 4 or 5 years old is sparse as far as I can tell). So no good for March/April unfortunately, thank you for the suggestion though!
Regarding the Visit USA ticket, does anybody know more, or would I potentially be better off to ask for that in the seperate airline subforums (unless that would be considered a double-posting, of course)?