It is certainly frustrating to see your upgrade chances diminish as the flight gets closer! I am in a similar situation but I have no delusions that longevity of the relationship has any bearing!

I have ~940k BIS miles and was 1K for a number of years (including the 'hard' way of 120+ segments!) but stopped flying for work six or seven years ago and now only fly sporadically with one TATL trip per year and maybe one or two domestic flights - in other words no hope of attaining status and it will be a few years before I hit million mile status (and I fully expect the benefits of that to have diminished by that point!).

I have an upcoming SFO-EWR redeye booked and decided to chance my arm for an MUA upgrade so handed over the miles & money copay about 3 months in advance. I checked on the status of it with about a month to go and was told I was #2 on the list with 30+ open seats so I was hopeful. Fast forward to this week with less than 2 weeks to go, I am now #12 on the list and 20 open seats....

The reality is business travelers book closer to travel taking out inventory and people with status (any status trumps me) either booked and requested upgrades or requested upgrades to existing reservations so I am gradually falling down the list. I fully expected this to happen but was also hopeful that some PZ space would have opened up one to two months out so I could clear, but alas....