I'm not frustrated, but I do wonder what the heck people are doing different to get so far ahead. I did go to Hawaii for 12 days, which limited how much I could check into the game. I barely made the last Broom gem reward for getting to 375. On the last day, I had to wake up every 3 hours and I made it to 376 on my last collection. Thankfully, my characters were running into a lot of 12 hour quests (maybe the ones your Mike & Sulley are doing now), or putting them on long upgrades, so I felt like I was making progress while on vacation, but I got behind on magic collection. I guess by comparison my characters are pretty good.
Maxed out: Mickey, Goofy, Tink, Woody, Jessie, Sarge (he's upgrading now)
Buzz has items to go to 9
Bo Peep, Hamm, 8
Daisy has items to go to 8
Mike 7
Celia, has items to go to 7
Sulley 6
Roz 4
Pete has items to go to 4