A 5 year warranty does that mean that the mattress is worn out after 5 years?
The warranty covers material and production mistakes it is not and indicator of how long the mattress will last. When the mattress does not feel comfortable and supportive anymore it should be change even if it is not worn out yet. Mattresses should never be passed on to somebody else. It may not be the mattress that the other person needs. And of course there is a risk that the mattress is actually worn out due to use.