Thank you very much for your answer.
You have given me a lot of information, but I have not been able to figure out all the details yet. I would appreciate your clarification:
... I looked at the Daily Save Ticket, it is already more expensive than STPflex, probably due to the fact that these are vacation days.
2. Tell me, please, until what time is the Swiss Travel Pass Flex valid - if I activate it, for example, at 10 am, will it be valid for a day until the next 10 am?
3. Did I understand correctly that the price of the Swiss Travel Pass Flex is not growing? That is, even if I buy it on the day of the trip - its price is fixed and it is always available for purchase?