Originally Posted by
Nirvana91
I never do EBCI, I always check in at exactly T-24 (and set alarms and calendar reminders to make sure I don't forget). If by some chance I receive a very bad boarding number (I consider any B to be "bad" and anything past B30 to be "very bad"), I'll go ahead and upgrade at the gate with either my WN business credit card or the $250 in travel credits from my Hilton Aspire Amex. In the few times I've upgraded I've usually been either A3 or A4, I think the worst I've ever received was A7. It's possible that you'd end up being on a flight where A1-A15 are already sold out, but I haven't seen it yet (although I agree that the fact that these credits now exist will make that scenario more likely).
So if you are able to correctly check in at T-24, that's probably your safest bet (if you don't want to pay for EBCI), and then depending on what number you receive, you can decide if it's worth it to upgrade or not. If you don't want to deal with checking in at all at T-24 it's a bit riskier, but you'd still probably end up fine.
Oh, another thing I forgot to mention. It seems that you can usually get the gate agent to tell you what position you'd receive, and also if your flight will have through passengers. So if something like the exit row or "infinity legroom" seats are important to you, that may be helpful to know. For example, I once upgraded on a flight from MDW-LAX because a) it was the first flight of the day and thus no through passengers; and b) the agent told me I'd receive A1 if I upgraded. So to me, that was a no-brainer since it guaranteed I'd get the infinity legroom seat for a long flight (since pre-boarders cannot sit in the exit row). If I'm remembering correctly I had already pulled a good boarding number at T-24, but in this specific instance it was well worth burning one of the free upgrades.