Have you tested the card to see how it performs specifically for what you want to do?
There are a few other limits that may come into play. One for instance is a single clip limit of 4 GB file size. You can immediately start the camera recording once that limit is reached. There is also a limit for a single video clip based on sensor temperature. From a Canon manual, "the maximum recording time of one movie clip is 29 min. 59 sec. Depending on the subject and the increase in the camera's internal temperature, the movie shooting might stop sooner than 29 min. 59 sec." Obviously a slow card will not work for a 29 min plus video clip. So there are really three limits you can hit, one, the file size limit of 4 GB, two, the 29 min 59 seconds limitation imposed legally, and three, a sensor temperature issue that might also be reached in some rare circumstance.