CSS files get cached with 30 days expiration period
The topic has been discussed here.
I am not sure whether this applies only to
::useStyleSheet() method or also to any resource related to
The preferred solution would imply a control over the "Cache-control" general-header field, of course.
As an option I'd suggest either a configurable expiration period (currently is a static 30 days) or the ability to define a content="no-cache" predicate to CSS files.