Having a user triggered reload after a workspace refresh, or switching between editors, in less than 300ms are also edge cases.

Typing a the first few characters of method or field, then hitting `Ctrl+Space`, without a 300ms pause in between, seems to me like a valid use case.
I tested locally, it looks like I'm fast enough to do it everytime without trying hard.
And if Content Assist Auto Activation is enabled (recommended setting), it happens everytime after typing a `.`.