You might want to say what location you are in for a truly useful answer. In the UK at least most providers keep the SIM active if it sees some activity in a g

You might want to say what location you are in for a truly useful answer. In the UK at least most providers keep the SIM active if it sees some activity in a given space of time¹ irrespective of top-up activity². So if “low” use stretches as far as one text every month or two maybe just have it send an “I'm still here” message regularly. Also acts as a double-check that not getting alerts means all is OK instead of that the alerting service is broken. 1: the GiffGaff one I used for pure data for a week-and-a-half when my landline was down in2020, shut off after three months and a few nagging texts IIRC 2: though if you don't top-up once per month you usually drop onto the basic tariff, so no more “unlimited texts”, but if you are topping up that infrequently that is probably fine