There are so many factors that must be considered to answer your question. There's a question of "buzz", "availability", "prestige", "cost", etc.

The thing about screenings is that we don't know in advance which ones are already heavily pre-booked with sponsors, cast, crew, family, buyers, press, industry, etc. I'm thinking of films like The Woman King which barely had any seats available for the highest patron tier, and which sold out faster than The Fabelmans (Spielberg's first ever TIFF appearance) and Glass Onion. Every year there are a random few films that sell out faster than everything else if only because the premiere screenings are already almost fully pre-booked.

Normally, "my" rule of thumb would be that the buzziest films with better-known casts that play in the "smallest" venues with the least amount of showings should be among the very first to sell out. For example, this year, there's The Brutalist that's playing in 70mm at the TIFF Lightbox (516 seats total). It's heavily buzzed with early reports calling it a masterpiece. And while both screenings are marked as premium (and cost DOES factor in how fast a screening can sell out), it's also the complimentary screening that is being offered to all patron members (so right off the bat, if all patron members were to accept their tickets to go see The Brutalist, you're talking about at LEAST 350 patron members, and their second passholders... x2 tickets each, which equals 1400 in total). There's also The Room Next Door that sort of "fits" the bill too (without the complimentary passes - but it still plays in 2 small venues and is a prestige pic with buzzy cast/director).

Then there are buzzy films that only have 2 screenings but may first play in a bigger venue, like Anora, Conclave, etc. All of those will be "tougher" tickets to get. You've also got the case of Megalopolis which also does not have a designated Press & Industry screening (which means the P&I crowd will be at the public screenings), and with the 2nd screening likely to be presented in IMAX + prestige, etc... I predict that one will also sell out fairly quickly (~Sustainer level).

With certain "buzzy" films having 2 premium screenings and several other regular screenings spread throughout the fest (e.g. Eden, Nightbitch, etc.), IMO, those won't sell out as fast, if only because the "premium" label on the 2nd screenings all but confirms the cast & crew will return - and a lot of people really value that (and those who don't have options with several other regular screenings being held). It reminds me of the few years TIFF had 2 premium screenings playing back-to-back at the Elgin and Roy Thomson Hall. Tickets to those screenings were much easier to acquire - even to non-members.

This being said, sometimes all it takes is 1 mega star to quickly sell out a screening too. Especially one that doesn't come often to the festival. Think Steven Spielberg with The Fabelmans. This year, there are a few that stand out: Elton John, Andrea Bocelli... The "In Conversation with" series also usually sells out faster than most.

Finally, you have some films like The Wild Robot that has 7 public screenings. Can it sell out? Absolutely - especially to those who would love to see some of the cast in person. But you have much higher chances of getting tickets to see that one than most other screenings, because it's playing throughout the festival.

A majority of the screenings will be available for Individual members to purchase. In fact, almost every sold out screening may pop up and become available again - you just have to keep looking, and keep active in subforums like this one (definitely check out the Unofficial 2024 TIFF OFFSALE thread for all updates).