OK, so how important is indoor training going to be for me this winter? I have access to spinning classes at the gym at work - hour long spinning sessions MWF and half-hour time trials and hills TTh. ...that's only 4 hours/week compared to the 10+ I'm doing now... If I make it to most or all of those sessions, or just go spin on my own a couple times a week, how much of my hard-won summer progress will I be losing compared to dropping a few hundred on a trainer and some videos? Indoor trainer: necessary livingroom furniture?