Running the risk of dating myself as a fossil, I remember prepaid was a service you buy for a year and top-up on-demand according to needs. Failing to use it or top up for a year resulted in the loss of service.
We often go hiking /skiing with the kids and I wanted to buy 2 prepaid SIM to put in a phone in each backpack we can use if/when needed... My first step: hit lycamobile.ch. My first shock: all services are now 30 days...
Question to the hive mind: do you know of prepaid cards that are a year in service, allowing one to buy and easily top up, not worrying the card /number may have expired?
Maybe check Coop Mobile prepaid? I've been with them for years. I don't add minutes or data very often - certainly not once every 30 days - and I've never been shut off. I do make calls from time to time, and receive an occasional SMS to remind me about an appointment. I looked on their website but my German isn't good enough to locate the fine print. Mr Wishes set it all up for me ages ago.
m-budget prepaid (migros) lapses after 12 months without use. They send 2 or 3 reminder SMS in a timely fashion, IIRC the first gets sent a few months or so before the lapse hits. Any charge resets the countdown, including sending an SMS.
The fees aren't particularly low but that shouldn't really matter for the occasional "I'll arrive at 5pm" half a dozen times a year.