I'll agree with the sentiments here:
- I don't think that there is a best time to check-in
- I agree to more often than not if you want the upgrade to a suite you need to ask for it. I find that room type upgrades to "view" or whatever happen regularly, but not to the standard suite
- Generally speaking, I like to online check-in early and then call the Front Desk to ask about upgrades. General philosophy being that if there are a number of globalists eligible, it's helpful to me to ask about it before the others.