We definitely could have ported the entire thing in under 22 months if that was our goal. The goal was actually just to make product improvements and gather customer feedback as fast as possible in the time we had, and the porting from PHP to Django just kind of naturally fell out of that. For example, the only PHP left for quite a while were the index and login pages. Until we actually needed to touch that code again for other reasons (a bit of a UI refresh), it didn't make sense to port that piece. It was working just fine and we had (and still have) a lot of other things that are important to work on instead.

Also, for about 2/3 of those 22 months, the development, operations and support team were the same guy, so that does have some impact :P