Haf
Do not consider any public transportation ticket in Switzerland as a reservation confirmation, because it isn’t. Consider a ticket just as an admission fee.
Therefore a „stop of bookings“ will never occur, even during busier times. Queues may occur though, but already having a ticket does not make a substantial difference, as Krist already mentioned above.
In rare cases, cableway or mountain railway operators may shut down operations due to adverse weather conditions, such as storms, landslides, etc. A more common scenario is that the summits are covered in thick clouds, making that the most expensive fog you’ve ever paid to watch in your life.
In both cases, tickets will usually NOT be refunded according to the T&Cs you’ve accepted with the purchase (force majeure etc.)
Are you now still convinced that buying such tickets weeks or months in advance makes sense?