I went onto the website to check some of my limits. I didn't have any offers right on the account summary page, but when I clicked on the link for all account services and then searched for "increase credit limit" i was taken to a page to request higher limits on my cards.

I made a significant (5 figures) increase to the limit on my Costco card and that was approved instantly. I then did the same thing for my Amex Blue and they said they would respond in a week (I don't really use this card anymore, but I keep it because it was the first credit card I got).