This is why we created the concept of "health checks" for Casa clients. No funds transfer required, just cryptographically sign a message with your key that we verify is producing the expected signature.
Discussion
Definitely a nice peace of mind check, good feature!
I read many clients store their keys in remote locations, so they have to get on a plane to get hold of their keys (or even only one key).
To do that every 6 months is quite an effort.