I had a minimally invasion double fusion a little over a year ago L4-S1). Unfortunately, it did not help the nerve pain in my legs and feet. Nerves can take up to two years to heal, so I suppose some might say there's a little hope left, but usually my understanding is people who are going to get improvement feel it within the first weeks, even though it might only start improving then.
Scarred is absolutely right about following doctor's orders. And I found that any recovery times they gave me (4-6 weeks) were much longer. It was six weeks before I even sat in my car and drove around the block. A realistic time was more like 3 months, but even now the muscles around the incision site tighten up very easily. I was told I'd probably have more back pain but if the surgery was successful I'd have significantly reduced or eliminated symptoms in my legs and feet. The trade off would have been fine, but instead I got the added back pain. Remember each person is different. If you've tried all other options and feel this is right for you, then go into it with a positive attitude.
On the positive side I was worried about losing a lot of flexibility, but that didn't really happen. There are certain moves - mostly a bend or an odd twist - that make for a sudden, sharp pain, but I feel I've actually gained a little flexibility because some things (like folding clothes on the bed) I'm actually able to do now if I'm careful. Before the surgery, that was impossible.
I was also unaware how much sitting for any length of time can be especially harmful after the surgery. I'm sure others will come along with info.,and you can search old threads. Many of us here have had fusions.