What is the recommended period or state for checking a motorcycle engine's valve clearances (tappet clearance)?

1. When the engine is cold (below 35°C / room temperature) and the piston is at Top Dead Center (TDC) on the compression stroke.
2. Immediately after running the engine for 30 minutes, while the components are fully expanded.
3. When the piston is at Bottom Dead Center (BDC) on the exhaust stroke, while the valves are open.
4. When the engine is running at idle speed, by listening for mechanical tapping noises.