I had a hip replacement 9 months ago and they have you up and walking, climbing stairs etc. the very next day. My recovery was so quick but the other hip became increasingly worse so now I have to have another one. I was cycling in the physio sessions, with the saddle very high, only 10 days after the op. They said the recovery was quite quick as my muscles were very strong as I had exercised up until the op. Hopefully this will be Andy's 'saving grace'.
I think the pre-existing fitness is a key point. In my case because the rest of my joints are wrecked because of my rheumatoid, 5 months after my hip revision (replacement of a worn out hip replacement), I still needed one crutch to mobilise.
I wouldn't be totally surprised to see Mr M appear and play a match or two at the WTF. Who knows, given non of us actually know what has been done? It's all supposition.
What I am sure of is he will follow advice. He will want this sorted properly.
I think the important thing to remember here is that this was an operation which, it's generally understood, involved a spinal nerve, and it's the very delicate nerve aspect which is so crucial. If it's been trapped it might have suffered some damage, and so will need time to heal, and, although it will now be free, it will also be sensitive, so trying to push things too hard could cause it to flare up, which would only impede healing and recovery.
The fact that Andy is already very fit should be of considerable help, but that doesn't mean that things can be rushed.
In this connection, please see excerpts from an article written by a sports physio in The Tennis Space which I've posted on the Recovery thread, which explains all this. Also the article can be read in full on - http://www.thetennisspace.com/tennis-physio-murrays-back-surgery-doesnt-surprise-me/