Toho... no limit on length for the cord, but, remember the requirements in 410.22. I've seen people get pretty sloppy with this type of installation.
Quote
410.22 Luminaire (Fixture) Wiring — General. Wiring on or within fixtures shall be neatly arranged and shall not be exposed to physical damage. Excess wiring shall be avoided. Conductors shall be arranged so that they are not subjected to temperatures above those for which they are rated.
