Not even say for $500k+ TC per year (not unreasonable today from faang)? Copyright for all pre-existing stuff stays with you, the question is just who gets IP rights by default to all the new stuff (including commits to existing projects) that you do while on that fat paycheck.
If they want the IP rights to my International Flatulence Database, I'll gladly plaster their name and copyright all over it.
Yeah you should never do that. It feels as it takes away a part of your soul and also shows how little they trust you.