I agree with this.

I think the amount of use makes a difference. Obviously, there is some advantage to using the tire enough that the sealant gets spread around. So, to the extent it does dry out, it is evenly spread. But, the more miles you put on a tire, the more punctures you put in it. Many times, I've retired a set of tires, especially front tires, not because the tread surface is worn out, but rather because the dozens of tiny punctures begin to start weeping. It's not sealant in the sense of what you get with a puncture before it seals. It's watery with no sign of latex (or whatever) and I suspect the main component of the solution the solids in the sealant are dissolved into.

I also suspect this relates to the tire casing breaking down to some degree.

Point being, I think it plausible that lightly used tires may go months without sealant drying up. Many report that here on BF. But that's not my experience with different tires and sealants. But I'm typically putting in around 500 mile per month. So a significant amount of mileage.

We all seem to refer to the time between sealant maintenance, but I wonder if mileage might not be a better parameter to relate it to. Rather like oil changes in cars. We use mileage not months. It doesn't seem unreasonable there is something happening to sealant as it is continually getting sloshed around while riding. And as mentioned, the tires clearly wear out and it seems reasonable this would affect the sealant.