Talked with a friend, 3.5 to 5 years is the normal time it takes men to forget if they really loved you and you said no. If you change your mind in *that* meantime, just come around, and try.
If they won't say yes, they didn't mean it. (but please, don't waste all that love just for some silly agenda or making sure we try hard enough. Keep in mind nice guys do take a no for a no. ;-)
And no - I'm not in a deep crush with anyone here, just wanted to share since we came up with roughly the same number.