Somebody had a birthday!
The 5th Edition of D&D was released on July 3rd, 2014, so it is exactly 10 years old (and counting). It's the second-longest running edition of D&D behind AD&D 2E, and it has the longest gap between rules revisions of any other edition.
- OD&D only ran for 3 years, and didn't have any rules revisions.
- 1E did not have any rules revisions either--it was the same 1E goodness for all six years of its run.
- Basic D&D was the first to get on the "revised rules" train. It was released in 1977, and was revised in 1981, 1983, and 1991, sometimes running different revisions concurrently. Seriously it's all over the place.
- 2E was released in 1989, and it was revised in 1995--a six-year gap.
- 3E was released in 2000, and then revised in 2003--a three-year gap. I remember this gap between revisions (or editions, if you consider 3.5E a completely new and separate edition of D&D) was so short that a lot of folks were outraged.
- 4E was released in 2008, then expanded in 2009 & 2010, and 4E Essentials were also released in 2010; I leave it up to you to decide if they count or not. Either way, this give 4E the shortest gap of all editions, at just one year (or two.)
- 5E was released in 2014, and won't be revised until later this year--a 10-year gap.
All of this came from Wikipedia, so swallow it with the usual grain of salt.
(I meant to post this on the day of, but I was out of town for the holiday weekend and didn't get around to it.)