Forgot to mention that seven years was also the traditional period of time for an apprenticeship, after which the young man would be free to set up business for himself - perhaps back at home where he left his truelove. 'The Bailiff's Daughter of Islington' makes this clear. Another point to make with a lot of these songs is that often she doesn't recognise him because he is so well dressed, having had 'made it' and then come back to impress her (which is why in 'The Poor and Young Single Sailor', for example, she says she is 'not fit to be (his) servant'. A final point is that where the young man is not recognised he often gives her a test to see if she is faithful to him, pretending that he is a friend of the dead lover and checking her reaction. As Eliza Carthy pointed out, his continency during the 7 years isn't usually enquired into!