I have to take a business trip in late January DCA-SEA and I was checking fares over the weekend. $313 for coach, but F is as cheap as $705.
Even though it's twice as much $705 for a transcon F ticket is worth it to me. I know the UG chances on this route will be slim or will be at the gate. Plus I'll get the MQM bonus.
I've given up on upgrade windows except on short hops or flights where I won't mind sitting in coach (normally short hops). Now I do my best to book F or use upgrade certs (some from choice benefits, some from SkyBonus) to push my way up the UG list.