348.20 (A)(2) limits some smaller sizes of FMC to 6' lengths.
356.12 (3) limits LFNC to 6' lengths.
360.12 (6) limits FMT to 6' lengths.
You should always check for local amendments that may have additional allowances or restrictions.
Also watch out for the 6' length limitation in 250.118 (5) if you're not running a separate grounding conductor through the flex. This is the result of UL only testing 6' lengths for their suitability as a grounding path.
