First - improvement and time:
Improvement is going to be very much a factor of time. But it's not all about time. 5 hours a day playing lightning when you are just pushing wood and not thinking about your moves is not going to get you as far as 2 hours a day doing hard-core studying of tactics and middle game ideas.
How much is healthy depends a great deal on what else you have going on in your life. If you're spending 8 hours a day doing chess after work and never seeing your family, that's probably not healthy. If you're single and unemployed and you're spending 8 hours a day doing chess between job interviews and as a way to keep sane in the evenings without spending much money, that's probably just fine.
Ultimately life is about choosing between options and for each of us the right balance is going to be different. But likewise for each of us there is a point where too much of a good thing becomes a problem. Basically, if the time you're spending playing chess is causing problems in your marriage, you might want to consider if you aren't playing too much. If you think you're playing a reasonable amount of time and that it shouldn't be causing the issues it is, then perhaps you have other problems in your relationship that might be worked out someplace other than an internet forum.
), but as with all obsessions problems arise when it interferes with a so called normal life. Is your job or your relations threatened? Are you taking time to exercise and eating nutritiously? I'm not a psychologist, but I have a feeling that unless you have serious underlying mental health issues most people can find a balance between their love of chess and their lives. Obviously if you are instead using chess as a neurotic coping mechanism, then there are problems. I don't think chess is the problem though; if you have developed an unhealthy relationship with the game then you have some underlying issues that need to be addressed. Of course many of us on this site might be considered "chessaholics" by the mental health community so it's a difficult call.
As most of us have learned Chess is obsessive.
Especially when you play with a live opponent. All activity around you seem to pause when you are engaged in a game of chess.
So how much of it is healthy, Psychologically (and Socially for those of us who are married).
And is improvement in chess proportionately related to the hours you play.