Investigating maintenance tasks that are best done with the bike upside-down Hoisting a bike on a stand makes almost any repair a lot easier. _A bike stand is the **third** tool you should get, after hex wrenches and a screwdriver_. Normally a bike is simply hoisted on the stand. When did you find that flipping the bike upside-down—either on a stand or simply on the ground, taking care not to damage any levers—is superior to regular (seat up and wheels down) hoisting (on a stand)? Do note that an upside-down bike (whether on a stand or any other method) is not recommended for hydraulic disk brakes.

Not many. During initial assembly of the bottom bracket area because access is easier when it is a bare frame and upside-down. This includes cable guides that mount under the BB.

If I was painting a bare frame, I'd do at least one coat with the frame upside down to ensure coverage of the hard-to-see areas. Same for sanding, and general inspection before painting the bare frame.

All other assembly or maintenance I'd do with the bike right-side up because gravity has an effect on the transmission and how it works and shifts.
The mass of heavy wheels isn't a problem if you're lowering the frame onto the wheels instead of lifting wheels up to frame.

I might also put the bike upside down when removing a stuck seatpost with a vise and leverage, or if I've had a roadside mishap and having to improvise.