There's many different ways with different performance tradeoffs. for example for my Homeland server I've set it up that I have to enter it every boot, which isn't often. But I've also set it up to run a ssh server so I can enter it remotely.

On my work laptop I simply have to enter it on each boot, but it mostly just goes into suspend.

One could also have the key on a usb stick (or better use a yubikey) and unplug that whenever is reasonable.