I have the front passenger side suspension leaking down all the way after 24h AND front driver suspension sagging somewhat, but not leaking all the way. I can still pump the car up, everything looks normal, then it leaks down as described after 24h. I had replaced the front passenger strut 4 years ago (all 4 corners), and then I replaced the front passenger strut again 2 months ago (FCP Arnott warranty), because front passenger was collapsing. It seems unlikely to me that the replacement unit is bad, especially because I'm seeing sagging on both front struts.

So my logic is that the leak should be common to the front axle, which points me to the valve block : is my logic sound?

(What confuses me is that I thought there was an air solenoid for each strut, such that once it was filled, the air solenoid would not allow air to escape. I would have figure a leaking valve block would make it hard to pump car up, but not to cause leaks while sitting?)

Your front air strut has a leak in the rubber bladder. Replace both air struts at the same time. After replacement, calibrate the air suspension.

I am just posting so I can keep track of this thread.