As I said in the previous post, you should allow at least 24 hours after submitting before upgrading, as this is the timeframe that ML takes to do its work. So, once 24 hours have passed, you can upgrade your nomination.
Personally, like I said, I usually wait until a nomination is in voting before upgrading. However, if I really want to upgrade, I tend to wait about 48 hours, just to be on the safe side.
This is in regards to this thread, if anyone is wondering: