I personally don't see how it can be healthy, even if it's done together.
I can't say that I could truly separate the fantasy part with the real world urges. Part of the fantasy of pron is that it usually is not the person you are married to nor anyone that resembles him/her. If you can extrapolate the situation and details and picture your spouse all the time, more power to you. You're better than I am.
I try to avoid it at all costs honestly. I love my wife dearly and I don't think that fantasizing about anything that we can't/won't do together is healthy.
**** is like movie romance. It never happens like that and can make the real thing tame in comparison. If it was just like real life, no one would watch it.