finding G availability

I had my first-ever disappointment with availability in G last week: I flew on VS 008 from LAX to LHR on the 10th in an L fare-basis seat in Economy, having failed to find availability in G, despite checking more than once per day every day and buying the L seat weeks before the flight.
The FC Gold telephone support line told me on the morning of the flight that there were 4 seats in J still unsold, and that to upgrade, I'd have to ask at the airport. Apparently, those all went to revenue customers on the day of the flight. When I arrived at the airport (uncharacteristically early, at 5 PM before a 7:45 PM scheduled departure), I was told that J was fully sold, and that there was a waiting list for upgrades in case of no-shows, on which I was second. I was never called, and don't know if the person ahead of me on the waiting list was. (If he was, I didn't hear any announcement in the Air NZ lounge in LAX.)
I've had very good luck with upgrades previously, on flights from LAX, SFO, and IAD. In fact, in 3 years as an FC Gold member, I don't think I *once* failed to upgrade after buying an L fare-basis ticket.
All of this leads me to want to learn to do a better job of catching G availability promptly when seats are released. I accept that if I buy an L seat when there's no G availability, I'm taking a risk that I'm paying more than I have to for an economy seat, and that no upgrade will ever materialize. I've not worried about that possibility thus far because it had never happened to me! No longer.
So, a couple questions to anyone who knows more about VS's inventory control than I:
1) Has VS tightened inventory in G this year as compared with in the past?
2) Is there a particular time of day when seats are released to G inventory? Can it happen multiple times per day? Basically, what I want to know is how often I should check and what time of day, to maximize my chances of finding the odd released G seat.
I'm wondering if I should just write a screen-scraping application that logs me into my FC account on the VS web site and checks G availability every 10 minutes using the standard FC web form, and emails or texts me when a seat becomes available...
All advice on how best to find G availability appreciated.
Thanks!
The FC Gold telephone support line told me on the morning of the flight that there were 4 seats in J still unsold, and that to upgrade, I'd have to ask at the airport. Apparently, those all went to revenue customers on the day of the flight. When I arrived at the airport (uncharacteristically early, at 5 PM before a 7:45 PM scheduled departure), I was told that J was fully sold, and that there was a waiting list for upgrades in case of no-shows, on which I was second. I was never called, and don't know if the person ahead of me on the waiting list was. (If he was, I didn't hear any announcement in the Air NZ lounge in LAX.)
I've had very good luck with upgrades previously, on flights from LAX, SFO, and IAD. In fact, in 3 years as an FC Gold member, I don't think I *once* failed to upgrade after buying an L fare-basis ticket.
All of this leads me to want to learn to do a better job of catching G availability promptly when seats are released. I accept that if I buy an L seat when there's no G availability, I'm taking a risk that I'm paying more than I have to for an economy seat, and that no upgrade will ever materialize. I've not worried about that possibility thus far because it had never happened to me! No longer.
So, a couple questions to anyone who knows more about VS's inventory control than I:
1) Has VS tightened inventory in G this year as compared with in the past?
2) Is there a particular time of day when seats are released to G inventory? Can it happen multiple times per day? Basically, what I want to know is how often I should check and what time of day, to maximize my chances of finding the odd released G seat.
I'm wondering if I should just write a screen-scraping application that logs me into my FC account on the VS web site and checks G availability every 10 minutes using the standard FC web form, and emails or texts me when a seat becomes available...
All advice on how best to find G availability appreciated.
Thanks!