Interesting hypothesis. It sounds reasonable, anyone want to try to verify it?

That seems way more likely than calcium build up.

Assuming you are correct...
Starting with a working filter and keeping it in a sealed bag or capping the ends would prevent complete drying. On the other hand after use it probably takes quite a long time to fully dry so unless you will be in a very dry environment for quite a long time between uses I'd guess it is unlikely to be a problem.