I'm a playwright, and here is my experience:
I was told the "page a minute" rule as well, and I do go by it. However, my mentor gently pulled me aside after looking over my eighty-page script and said, "Because of the way you use language, this play will run about two and a half hours." When actors cold read it to me, and they were doing it quickly, it was a little over that. The play was quite monologue-heavy at the time and over a quarter of it was stage directions. I took the (wonderful!) advice given and cut it down to fifty-three pages. I have no idea how long the current draft will run.

So, what I am trying to say is if your script is monologue-heavy, the 1:1 ratio may not work. I looked over everyone else's responses, and (took a bunch of notes! Wow!) hope that my experience could be of use, as well.
I'm cheering you and your script on!