In order to make NICI as stable and self-healing as possible, NICI creates a local backup every time it is successfully ran. The advantage of this is NICI can often automatically detect and recover in the unlikely event of data corruption. The fact that NICI configuration and data files are generally fairly static, means that in most cases no data will be lost even if an automatic recovery is needed.
Although the fact that NICI creates a local backup will eliminate most data corruption issues, it is recommended that you continue to regularly perform an off-line backup of NICI.