Is it safe to drive a chevy volt(2018) on L-gear all the time?

I've got a cool story about this.. I took my Volt (14) to Colorado for a trip with my family and we drove up Pikes Peak. It gets pretty steep in some places on the road back down (so much so that they perform a break check 3/4 of the way down at the rest stop) With the Volt in L and mostly coasting back down I found that the battery had completely recharged by the time we made it back to the entrance gate at the bottom! Just from regen. Crazy right?