Currently, the OSHA 10 card does not have an expiration date associated with it. Most companies will require that employees retake the class every 3-5 years depending on who you work for (or who your company is working for).
While the OSHA 10 card does not expire, the topics covered during the class have annual or bi-annual refresher training required. This means that if you take the OSHA 10 course one year, you will have to get training on most of the topics either every year or every other year.
*Unless specific citations are shown, all answers are based on interpretations provided by authorized officials. As such, all information is deemed reliable, but not guaranteed.