I had a quick peek at the list of Elite Four for the second fight (the one you have after getting all of the Kanto badges) and I noticed that they get much more badass. Plus their beasts are leveled to the 60s-70s. After glimpsing at that, I'm thinking of leveling up my team on the old Elite Four a few times before getting my last few Kanto badges.
Kanto is funny this time around, because I've bumped into trainers in the forest who carry level 60 Metapods!!! No joke. They still only know 'Harden'. Totally harmless, but worth a ton of experience. X3
My creatures are 50s to late 50s, so it shouldn't be too long before I'm ready to do the second round of Elite Four. I also caught the Snorlax yesterday (which had been blocking the cave entrance), it's Careful natured and Likes to Thrash About.