But it is true.

In a big company, the VP of whatever department may feel bad about a layoff before Christmas, but they don't know you personally, and whatever numbers or major investors are motivating this don't lie.

In a small company, the same is true. They might wait until things are hopeless instead of trending to hopeless, but either way, they'll lay you off when it makes sense for them.

You might like your boss, but informing them well in advance of a departure is generally not a good move. Nice as they may be, they can't unknow that knowledge, and it will affect all their decisions going forward. And you, who are so sure you are leaving, may find that your outside offer is rescinded the week before Christmas (see above).

2 weeks is a reasonable courtesy and an acceptable risk. If your company needs you beyond that, contract billing should start at 5x your salaried rate, 20 hour minimum.