This is the reason why I no longer have VPSes at DigitalOcean, sometimes I couldn't update my CentOS kernels when important updates were available because DO lagged for a few days in making them available.
Ubuntu DO instances have a modified apt sources.list file that points all apt requests to a DO-run repository. If you revert to the default repositories, you should be able to get updates as they are released.
Not sure if the same applies to CentOS.