The date I wanted for the TOTP sold out last year (October 3), but it was largely my fault that I missed out on ordering tickets because I waited a long time to decide if I wanted to go to the TOTP or not. Fortunately, by the time I made up my mind and realized they were sold out, another person came through with some tickets for me, so I was able to go on October 3rd after all. So what I would say is that they won't sell out right away, but don't count on them being available last minute. It will take a good long while before they sell out, but I think expecting them to be available a couple weeks before the date you want to go may be expecting too much based on last year. Because once one date sold out last year, many of the other dates followed suit rapidly. Sometimes, though, you can still get tickets at the ticket booths on the day of the TOTP, but for a higher price.