I absolutely miss some of my old routes - even the ones that I cursed every mile of while I was actually running them, because they seemed so uninteresting. I used to live in a medium-sized city and I loved discovering new neighborhoods and new connections between old neighborhoods; I can still remember the Lewis-and-Clark-ish excitement of popping out of a forested park into a neighborhood that I would never have expected to be there.
But now I live in the rural NE, and there are so many different pleasures: the quiet, the hills, the ability to run TO ANOTHER STATE and back, the cool state parks that pop up here and there...Everywhere you go, as you know, you'll figure out new routes that will inspire and motivate you.
Part of what you miss is youth - those runs are as unrunnable as your youth is ungraspable. It's natural to be melancholy about that. Keep reaching for the pleasures of the here and now, though. As Edward Abbey said, "Heaven is home. Utopia is here. Nirvana is now."Good luck with your move, man. Hope the trails are good and the memories you form there are even better.
(And a quick side note: I discovered a new route the other day near my house and as soon as I was in the most beautiful part of it I started to miss it. Pathological! When I got home I coerced my wife into driving back out there with me; we spent a gorgeous evening by the river I had stumbled upon that morning. All I'm saying is, I can relate.)