Timeline Out of Whack
Whist I understand the urge to set the flashbacks in the 80s (so much fun with the music and clothing) the fact is, it dosen't work out mathematically. If they were all in their 40s in the present timeline, then the high school scenes should have been set in the 90s. Not to mention Ben referred to their glory days being 15 to 20 years ago - which is the early 2000s.
Ultimately, it would have been more accurate for them to be wearing Levi 501s with flannel shirts and long grungy hair, rather than stonewash skirts, fluorescent tops and crimped hair-dos.