I had OHS on 25 Aug 2009 with an On-X valve implanted in the pulmonic position, so I'm just past the 6 month point. At three weeks, I was still really tired and hurting, especially when trying to sleep. I walked every day but was still fatigued quite easily, and was still retaining a lot of fluids at that point, so the Dr. gave me a short dose of Lasix to help - about 10 days worth. I felt like I should have been doing more at that point, but like other people have said, listen to your body. If you feel tired, rest. Rest is the best prescription for healing. I remember at three weeks I was still having short intakes of breath and hating the spirometer to increase my breathing ability.
A good tip I read (can't remember where) was that a really good way to chart your progress is think about where you were one week ago, and then compare it to how you felt two weeks ago. Instead of seeing it as day-to-day improvements, which are so small to identify, it was giving myself a longer timeframe to compare. That helped a lot. Another thing that helped is I was using facebook to update my friends and family about my recovery, just short entries and usually a family member did it for me since it hurt to sit at the computer. I'm glad I did because almost the first 2 or 3 months after my surgery are a complete haze to me. By having those little updates - even if they were short (slept 4 hours), it helped me keep a record so I can see the progress I've made (now sleeping more, maybe 6 hours, which is low for me, but the most I've been able to get bc of soreness in my chest).
Lots of good thoughts!