What's the Average Recovery Time of Breast Reconstruction for a Mastectomy?

This varies a little depending on whether you are having an silicone implant reconstruction or one using your own tissue from elsewhere.  The implant reconstructions tend to have a slightly shorter recovery.  The operations take 2-4hrs and most people stay in hospital for at least a night.  After that you'll be home, pottering around the house, making yourself some food and ok getting in and out of the shower, but you'll probably want some help with the shopping and heavy housework for the first couple of weeks.  You should be back to doing pretty much everything you usually do by 4 weeks and feel virtually back to normal by 6-8 weeks, although you'll still probably get the odd twinge.  Your new breast will still take some time to get used to.
With tissue reconstructions the operations take 3-6hrs and usually involve at least a couple of nights in hospital.  You'll then have two sore areas whilst you are recovering: your new breast reconstruction and wherever your surgeon has taken the tissue from.  Whilst you'll be at home doing and recovering in a similar way to the implant patients, because you have discomfort in two areas rather than one you'll be a bit slower to get back to normal.  It will probably take you around 8 weeks, but for the first couple of weeks in particular you'll need a bit more help around the house.  
If you have any complications such as wound healing problems this might be slowed down a bit, although most of this has usually resolved within the same time frame.  Good luck with it all!

Recovery time after mastectomy depends on the type of breast reconstruction you undergo, and can vary by the patient depending on the overall status of your health and whether you've undergone a bilateral or unilateral mastectomy.
For patients who have had a tissue expander placed or who have done a direct-to-implant reconstruction following mastectomy, I typically recommend 4 weeks off work. If your job is very physically demanding, then 6 weeks may be more appropriate. 
For patients who have undergone a living tissue reconstruction, such as a DIEP flap reconstruction, I also recommend 4 weeks off work. For older patients, those with higher BMIs, or those with a poor overall health status, 6 weeks is definitely more appropriate. For those with physically demanding jobs, such as nurses, childcare workers, gym instructors, or policewomen, up to 8 weeks off work may be appropriate.

Breast reconstruction recovery can depend on the type of reconstruction performed- generally, implant based breast reconstruction will have a recovery time of about 4 weeks.  When using your own tissue (either from the abdomen or the back) recovery time increases to approximtely 6 weeks-- keeping in mind other patient medical conditions, prior radiation treatment may cause healing time to increase... best of luck