Using the loading attribute as the sole approach for lazy loading will be the recommendation once WebKit and Safari implement support. For now, though, it should only be used as an enhancement and not as a replacement for existing strategies.

This is an experiment to see what amount of delay is too annoying for a user interaction like typing. Here are some presets; make sure to type a lot of characters at once for the full effect.

A great tool to wrap your mind aroung the values of your First Input Delay.