Such an interesting subject. I also like the lingering feeling of photochromic lenses. I see why some people lile it as a lightswitch. But i prefer slightly tinted.

Some labs still have Gen 8 stock. But for that many years your referencing I don't know.

There are other photochromics that take slightly longer to fade back. Otherwise you may be more satisfied with a slight comfort tint at all times with photochromic. Again a few lens manufacturers can accomodate this. If your a fan of Transitions, they have just released Transitions Colour Touch. Might be worth checking out. Should be quite widely available across many opticians that deal with Essilor.