As this is a thread for newcomers to Japan, here is MrLapLap’s explanation on how many companies in his country add value and status and appeal to their products whilst keeping the reigns on the monetary cost to the customer: exclusivity. Queues are great marketing tools, and in this time of shrinkflation, the most cost-effective way to increase the value a customer places on an item is to increase the effort (and not just the know how) needed to acquire it.
This has always been baked into the Japanese economy but, with less staff and rising costs and a customer base seemingly willing to play along and contribute their time and effort in increasing the value of products and services, it’s as much the time and effort to the consumer that is increasing as the shrinking of the products and the rising of the prices.

When is too late to arrive? Popular items come and go at Bakeries, each company finds its own way to incentivise their customer base and maintain/increase profitability.
Whether it is getting seats on certain trains, in certain carriages, booking slots at museums, finding a place at a lunch venue, acquiring a particular bread or pastry, even ordering a coffee, it’s either easy and straightforward or more tricky and inconvenient than ever.

As Q Shoe Guy puts it, the option is often to “turn on a dime” or find your peace with alternative choices (place your value on what you have rather than haven’t - very easy to do when there is a yellow discount sticker on it!)

Simple answer to the question is that Mont Thabor closes at 9pm. There will be products on the shelf right up to the point it closes.