I'm 6 weeks post op, (my 2nd MVR). I'm in my second week of rehab, & doing great. I did not do it the first time, but I am this time, because I wanted to know that I was pushing myself far enough, and that I could safely push myself to my limits. I have a very physical job.
I doubt I will stay in rehab for longer than 3 weeks total. To me it has been worth it.
They mainly have me doing 40 minutes of actual workout, on a treadmill, bike, etc, anything that keeps the heart rate up, and this can be broken up between the above listed.
I have a treadmill at home, and I do walk for warmups, almost every day, but at this point, I'm not pushing myself at home as much as I am in rehab.