My Couch to 5k update to version 1.2 went live in the App Store last week, and this week sales are down 40%. Coincidence? Maybe not. When a new version comes out in the App Store, its reviews and ratings are all reset on the description page, so if your app had lots of 5-star reviews and ratings, it’s all lost until your users write new reviews and make new ratings for the new version.

If your app has a lot of competitors, those ratings and reviews are what separate you from the rest. Someone looking at your new version will think your app is new and untested.

It used to be that the App Store advice was to update often to get on the “new releases” page and get a corresponding sales boost. Today, with the volume of low-quality new releases, having good reviews is more important, so you had better make sure your version 1.0 is complete and polished enough to get good ratings, and if you already have a 5-star app, don’t update it unless there’s a major bug to fix.

Maybe this week was an anomaly, but previous updates to Couch to 5k and Couch to 10k have never resulted in more sales right after the update was released. In fact, the opposite happens: there’s a sales dip for a couple weeks before they return to the previous levels.

From a customer’s perspective, it’s annoying to constantly have to update your apps, especially if the update doesn’t fix any major bugs or add any new features.

I have over a year of sales data on Couch to 5k and other iPhone apps, and I have over 10 years of experience in selling Mac software, and the iTunes App Store is very different from the Mac. On the Mac, you add features and fix bugs incrementally, releasing a new version as often as every 2 weeks, and sales increased because news of the update gets around to VersionTracker and blogs and web sites. So you would update early and often. And major new versions (2.0, 3.0) would result in huge sales spikes from people upgrading.

In the App Store, that no longer works. You have to come out with a fairly complete and polished version 1.0, and if you do have a hit, you have to limit your updates to a few times a year in order to preserve your ratings and reviews.