Whenever I plan to cut it close, I always make sure I use OLCI.

I know about missing flights though! In November I got up to the security line, and was looking for my wallet, only to find I didn't have it. I had done OLCI, and only had carry ons, so hadn't needed it before then. Talk about a mess! Rushed home, finally found the wallet, and then back to the airport, only to have barely missed the only flight that would have connected. Luckily the NWA people were helpful, they pushed the e-ticket to Delta, and at least I got to my destination, sadly in coach, as all my upgrades went "poof". I won't even the mention the Barbie Jet.