I had my SR20 sitting in my garage for about a year but the swap it self took almost 3 weeks only because I instantly put a new clutch in, upgraded the turbo and the FMIC took a little while because of the pipping and re bar and all that shit. And it was worked on a few hours per day. If it was just a straight swap it would of been done in like a week.
From when I bought my car till when I put plates on it and drove it, about two years. In which I swapped an SR and a bunch of other stuff. This is my 3rd summer driving it with the SR, it saw maybe 1 km on stock motor/exhaust/suspension/diff while I owned it.