Has anyone noticed that their lather tends to get thinner in the brush as the shave progresses?

This has been happening to me more lately. I lather on my face, and when I set my brush down in my Moss scuttle or latte mug, it seems like next time I pick it up the lather has thinned noticeably.

I get nice fluffy lather to start out, so I'm trying to pinpoint what's causing this.

Anybody else notice this and figure out a way to lick it?

Josh