How stable is in vivo whole cell patch clamping?
After talking to a few electrophysiologists, I found out that they have very diverse opinions.

It seems that a common way of stabilizing the movement of the brain with respect to heart beat is to press the brain with some softish-rigid material like agar. Also, draining the CSF could help but then this cannot be done without sacrificing the animal.

The quality of the patch degrades over time, and it could be held for an hour or more (anecdotal).