I find that as I've grown older, I have less time to commit to friends (wife, kids, work, house, etc). It's harder to spend the time to make a new friend. It's not like being a kid, having no responsibilities yet, and hanging out with friends a LOT. You don't have a lot of time to get to know new people.
It's very comfortable to have those old friends. The ones you're already established with and can just pick up with when you get together. You don't have to commit the time to deepening those friendship like you do with new ones.
I also appreciate having that common JW background. But I no longer have any of my old JW friends. I do still have my brother who also dropped out of the JWs. When I need a live face to talk with about those things, there's nobody who shares more of my childhood and all of those experiences with me than my brother. For other JW things, there's always this board.
I don't know what to suggest. I know that many of those friends wouldn't be your friends if you left the JWs. You can say that doesn't make them true friends. But that depends on your definition of friends. Being able to reminisce about old times? Just being able to hang out? If your needs are simple and they satisfy those needs, why replace them?
Some of my oldest and dearest friends, I don't share my deep thoughts and concerns with. When we get together, we hang out. We watch football, go out for beers, talk about what's happening with people we know, etc.
New friends can replace some of that. But it's going to take the rest of your life to build up the same amount of common ground that you have with your current friends.
But the problem is this: You are already flirting with trouble in your congregation. It may be that you could end up being labeled an apostate in a year or so and you'll lose all of those friends. In the long run, it's better to start disengaging from them and replacing them with others who will not leave you based on things like this.
Without planning it that way, that's what I did. I made worldly friends throughout school. When it became time to leave the JWs, I had other friends. It wasn't as much of an emotional disaster. And I didn't end up feeling the need to come back due to friendships. Family was a different story. But I had other friends.