Originally Posted by fmsm

Yes it does effect you.

1) By checking in early you are taking yourself off of the "request upgrade" list that is controlled by the main system. If somebody that has received an upgrade already changes their flights (sdc) and the v or x inventory is returned you will not be upgraded even if you would have been next on the list.

2) Your only chance at upgrade now is gate controlled.

If I have not cleared an upgrade by the 24 hr check in window I will wait until 3 hrs before flight to check in.

Of course some of the other factors mentioned earlier in the post do apply.