Mornings in the Mountains
Personally for me, mornings are the most difficult time of the day to capture time-lapse videos in the mountains. Getting up early is never the issue, but leaving the cozy warm confines of your sleeping bag takes a lot of effort and willpower. 

My routine is always to get up in the morning, open my tent and take a peek outside while still inside my sleeping bag. I would get out of my sleeping bag if and only if the weather outside is perfectly clear and i'am confident of getting a good shot. Otherwise it is just not worth it.