Finding United upgrade space

In late 2023 I subscribed to a new service called Seats.aero that constantly scrapes airline websites looking for real, bookable points and upgrade deals. They have a slick United PlusPoints upgrade finder which I quickly discovered also finds instantly-bookable Mileage Upgrade Awards (MUA). Given how expensive it is to make 1k and get a basket full of PlusPoints, this discovery was a game changer. 

Ideally we always want to have our upgrades confirmed at booking time. Given work schedules and holidays we sometimes have book a flight without confirmable upgrade space and hope for the best when flight day comes. Tim and I have both had instances where, despite being 1k and using PlusPoints, we didn't get an upgrade because all the seats were sold or they were given to people with higher status. The big downer of my new strategy is that in these instances, we'll be even further down United's elaborate upgrade pecking order (i.e., a 1k requesting a MUA will lose the upgrade to a Silver using a friend's PlusPoints).

We're halfway through 2024 using this technique and I feel like I want to leave myself some historical notes about availability for future years (assuming Seats.aero doesn't get sued into oblivion). I'm going to periodically update this page so I have notes for myself for next year.

• USA to Australia. Unsurprisingly, lots of availability in the off season (May – Sept). Flights to Sydney had several days each week with PZ1 - PZ5 with multiple dates. Availability was from "today" to about about six weeks out. New dates show up every four or five days, usually at the end of that six week window. Flights to BNE and MEL had dates farther into the future (around 8 weeks) but because fewer flights operate to those cities there were fewer dates to choose from. 
• Australia to USA. Going the opposite direction had a similar dynamic, but a shorter window – four weeks out instead of six. 
• Both directions I noticed that furthest-out dates would open up, and then several days/weeks later new, earlier, "in-fill" dates would appear. 
• FYI the Houston–Sydney flight operates from November to March

• Okaaaay note from early August -- United has canceled about half of their flights to Australia due to poor demand. Further, they've added Australia as part of some new promo that looks like a lotto scratch ticket. I still don't have a mid-September flight home from Sydney booked and I'm starting to think I might not find my green checkbox. 
• Like there are dates for August and October but September is pretty much empty except for one flight from Auckland. For now I'm just holding my breath hoping one of my alerts triggers and I can snatch my seat.
• I also need to find a way to book things where it doesn't take up so much mental energy to plan it out. Like I get that nothing's free and some amount of work is required to get a $10,000 ticket for $1200, but I think it might be best to just book my plan B flight, be at peace with a 2-stop itin, and then if I get a seats.aero email about my plan A coming available it's just a nice surprise. I don't want to be on here poking at flights every single day, y'know?

• ANNND of course the SYD to SFO upgrade I'd been waiting for became available literal day after I got my entire "Plan B" trip home (via Auckland) booked! Arrgh! (Aug 9th for a 17 Sept flight). I'm actually going to keep things as-is and enjoy a couple of days in a new city, but I wanted to note how the inventory is being released for future reference.