I'm flying ATL-SFO on a Monday night 10:00 pm arriving 12:25 am. From what I've read, upgrading on ATL-SFO is extremely difficult. Added to that, I'm just FO. So, two questions:

First, given that it's a late flight... are my upgrade chances somewhat respectable? Or still a long long shot?

And second, G inventory is available and K fares are around $85 more than the LUT fares, so I could upgrade for $85 and burn 12,500 miles. So, second question, is $85 and 12,500 miles a reasonable price to pay for this upgrade... or would you suggest keeping your fingers crossed for the upgrade and just plan on dealing with economy at that price point?

It's a 757-200 if that makes a difference.


EDIT:

Having returned from this trip I thought I'd provide an update. I decided to book a T fare ticket based on the responses below. Although it seemed that I wouldn't likely get a complimentary upgrade, the cost in miles didn't seem worth it. To my surprise, I was upgraded... at my 24 hour FO window. And while it was especially nice up front, I would agree with some of the posters below that 12,500 miles for the upgrade would not have been worth it. So thanks for all the insight. It saved me a few bucks and a few thousand miles!