Well, i was doing a single tank dive on air the other day for 2 hours at 500 feet and the buttons worked great!
What are you doing down there...I assume you must be a tri-mix or heliox technical wreck diver or just a deep junkie:)
The housing is rated to 300 or so feet so that should not be an issue. There is plenty of spring in the buttons i have observed. I believe they pressure test in a tank below this depth.
Your issue may come with the 80degree lens if you get this. I recall it is limited to a shallower depth (maybe 200feet). I have seen this to be the case with several other wide lens. At that depth you will be 100% on lights so a wide may not be necessary regardless...you won't have a wide FOV anyway.
I would ping L&M with this one.