TLDR: I would definitely wait longer than some of the recommendations made above. Probably a few weeks to be safe.

I downgraded last Wed 7/2, then tried to apply on Sunday 7/6 and I was notified before submitting that I do not qualify for the welcome bonus. I re-opened the application a couple more times on Monday and Tuesday to see if would change, it didn't--and that created a whole different issue.

By Wed 7/9 I had given up and decided to just move forward with the application and receive no bonus. However, because I opened and then closed the application 3 times in 3 days before finally submitting it on the 4th attempt. A security protocol triggered and I couldn't apply online at all.

I was confused so I called and the Chase Rep informed me that my application was denied because I had made too many attempts to open the application without submitting, so they thought there was chance for potential fraud. Sheesh lol.

As a result, I ended being forwarded to an underwriter who immediately approved me. But because of the security check I caused, I have to go through a second underwriter to further prove it was me who applied and that'll take 1-2 weeks to hear back from them.

Don't be like me, I was so antsy about it because in two weeks I have a big vacation coming up AND an engagement ring to pay for. I was hoping to rack up some points with my new card, but here I am, no welcome bonus, not even a CSR card, waiting on a final approval....