I fly Alaska's SFO to HNL route monthly as a 75K. Usually upgraded to F around T22-18, occasionally T30s. At the 120 hr upgrade window I noticed 7 available F seats with the Blue available upgrade mark on the website. Around 12 hrs later I checked my itinerary and was still wait listed. I called Alaska to inquire about the 120 hr window. Was informed CSA could not do anything about it as upgrades computer generated and that I could use a guest pass upgrade to guarantee an F seat or wait a few more hours for the upgrade. With 7 seats open I told her I'd wait the few hours. I checked a few hours later and the Blue F was no longer available . As F seats were now done to 5, I'm guessing 2 went to guest pass upgrades. This is probably the 3rd or 4th time I've experienced this the past 2 years. Similar experiences?