You should not be able to mess things up by setting back and forth. The only time you should get into trouble is if you inadvertently power off while in read/write mode.

All you are doing with the RO command would be to remount it as read only. You can do so repeatedly, and it will not cause any trouble. All you might do (if you do it a lot) is increase the mount counter for the filesystem, so that if you are not suppressing that check through hijack, your syncs may decide to do an fsck based on the number of mounts.