From what I can tell, there is no single recommended way for creating the questions of the form "When will X happen?" I see several patterns for questions like that and I'm not sure which one to follow for my own questions.

First option is to create a group of separate questions, all linking to each other, like this one: https://manifold.markets/RemNi/will-we-get-room-temperature-superc-f41118c07313. The downsides are: a lot of work for the question author, hard to keep all the questions in the same place. (BTW, how does one link to a question with its current probability?)

Second option is to make a multiple choice questions with mutually exclusive answers like this: https://manifold.markets/t3ss/when-will-the-rabbit-r1-stop-workin. The downside for me is that it's difficult to reason about the probability of something happening in a specific period in the future.

The third option is a multiple choice questions with non-exclusive options "X will happen between now and Y". Example: https://manifold.markets/OlegEterevsky/when-will-valve-announce-a-standalo. This format is informative and easy to reason about (at least for me), but the votes on each option are independent, which means that it's possible that the probability for the later date will be lower than for an earlier one.