he has definitely fallen asleep down there before.
on that note: sans kinda sleeps a lot. he has insane magical potential, but his body just cannot keep up with it, so he wears himself out really quickly.
sans is actually kinda comfortable in the lab and doesn't touch things he isn't supposed to in there cause it knows it could be important. he usually sits down there and plays nearby his dad so they don't have to be apart so much