@ascentale @gcvsa @bikenite #BikeNite A7. Under 24 hours if it's at work (widely perceived as a safer place to leave a bike, and semi-restricted access), for my nice folding ebike. Anywhere else I would not leave it after dark out of sight, even though Hamburg seems to have much lower bike theft than anywhere I've lived before.
In Eugene, Oregon, I would not leave *any* bike outside and visible, but out of my sight, for more than a few hours and I'd be very particular about where I locked up. I'd lock the frame and both wheels (this took two locks) to something embedded in concrete. My sister has had a bike stolen in a ten minute window in the middle of the day (on campus) and at least three bikes stolen overall, plus at least one seat. My bike there was a very standard, heavy steel commuter, tagged with bike registry stickers and registered with campus police.
In ths SF Bay Area I relaxed my standards slightly to locking frame and one wheel with a single lock, and keeping it in the most well-lit and well-traveled place I could find. I'd still never leave it overnight anywhere but work or home, and never on campus after dark. I still had lights stolen repeatedly, whenever I forgot to take them with me.
The great advantage of bike lockers is no one can even tell they're occupied without breaking in! In Eugene you could rent one long term some places and on an hourly basis in several locations around campus. Absolutely my preferred solution, and I'll park further from my destination to use a bike locker if it's available.