Only two years. That still leaves four years of development, which is kinda long. And even if you take off the 1.5 years for beta testing, that's still 2.5 years of FREDding.
In reality, of course, there were no such clear demarcations between project stages (i.e. "this is FREDding", "this is testing", "this is voicing"). There was a lot of overlap, and a lot of rework. The readme expands on this topic a little bit.
And thanks, unsrm, for your comments.
I do think ST:R is the better for having had that many years of polish. I wish it hadn't taken so long, but at least now it's released!