Originally Posted by Phil_gretz

The OP fails to give details like: where/what location, or duration (especially if overnight). So, many answers cannot apply.

My commute is onto a large Gov't installation that is quite safe (controlled entry points, guards, patrols, etc.) relative to a normal center of town or city. I still leave (permanently) a heavy chain and key lock at the bike rack outside of my building. It's been there for five years now. In my environment, this is likely overkill. I have seen bikes left unlocked and untouched there during work.