In terms of the 8 weeks out, I had my replacement 5 months ago and everything went great (52M, active). I was well into recovery at 8 weeks out but although I was walking close to 10 km per day at that stage, I still had some aches, pains and some severe sleep issues (which can be common). So, in my own experience anyway, I was doing well at 8 weeks but I wasn't back to "normal" for about 3 months.
For me, the physical recovery went very well by 8 weeks but I found the "mental" recovery tougher (by mental I mean not sleeping, stressing about the odd ectopic that could spiral into being convinced that I had Afib as a result of my subconscious making me feel loads of palpitations which weren't real at all but felt real to me, trying to get used to the new sensations and sound changes when lying on pillow for instance, lots of stuff like that which can be quite draining).
I had focused on the physical recovery beforehand but be prepared for some mental recovery too. Again, that's just my own personal experience but I found that I was much better recovered physically and mentally by three months. In fairness, I'd have to say my sleeping still isn't great after 5 months and I'm still prone to the odd over-reaction in my head to a skipped beat or something but I dont panic about these things any more.
After a long rambling post I suppose what I'm trying to say is that you might well be fine at 8 weeks out but it's difficult to predict for sure whether it's too early or not. Even though my physical recovery went very well, I'm not sure if I would have been up to it at 8 weeks, 3 months yes, definitely but 8 weeks, I dunno. Not sure I'd have enjoyed it as mych as I should. I think it all depends on your individual recovery.