If you can take several months off, it just means the company doesn't really need you. ...
Yes, but your comment is just plain wrong-headed, frankly. Small companies really, really need their employees. Departure of a key employee can sink a small company.
A large company like facebook has people leaving ALL the time. People retire, quit, move, change jobs, get sick, die and so on continuously. Any company over about 10 people is going to have to deal with departing and absent employees on a regular basis. You absolutely cannot have key employees for a large and/or long running organisation.
So yes, they don't "need" you, because they can't afford to need you: if the company is successful you'll probably leave long before it folds.
Or, it means someone else is will have to work harder (with no extra pay) to make up for your absence
Well, there's a sucker born every minute, I guess.