Ferret Health Question?

My ferret has been lazy all of his life. He's never really had that high energy that some other ferrets do. But recently, he's been acting a bit more lethargic. For instance, he only gets up to eat, go the bathroom (so to speak), and drink water, then he goes back to bed. Unfortunately, a few days ago I did notice some vomit in the ferrets room (however I have not been able to pinpoint if this vomiting came from the ferret in question, just mentioning it). Is this increased lathargy something to be worried about or, as he is aging now around 5, is it just an age thing?