We all know the story of Han Solo being a guinea pig for the planned freezing of Luke Skywalker, but how often are people "stored" in this way?
I wouldn't say people are "stored" this way very often. I'm sure there are instances of people being frozen in the Star Wars universe off-screen that we'll never know about because there are a lot of bad people out in the Star Wars universe. However, it has happened, in canon, prior to Han Solo being frozen.
In the Clone Wars episode The Citadel (season 3, episode 18), a team consisting of Obi-Wan Kenobi, Anakin Skywalker, Ahsoka Tano, and some clone troopers voluntarily underwent carbon freezing in order to infiltrate a planet that utilized lifeform scanners as a security precaution on incoming ships.
They were unfrozen by droids led by R2D2 when they arrived on the target planet.
By my count, this mission consists of about 8 people. Add Han Solo to the mix, and there's been 9 instances of carbon freezing people in on-screen canon.