After reading NEC 350.10 I believe there is no limit unless it is used for a service-entrance feed.

Now per NEC 356.12 the LFNC (non-metalic) is limited to 6ft.

Is there a lenght limit for LFMC (metalic)?

In general there is no limit on the installed length of flexible wiring methods except for Flexible Metallic Tubing (Article 360) and types A and C of Liquidtight flexible nonmetallic conduit (Article 356). The other flexible wiring methods can be installed in unlimited lengths, subject to the 360° between pull points and the support rules for the raceway involved. Remember that in counting the degrees, every little variation from straight counts, and this will provide a limitation on the installed length.
Don

Thanks for the confirmation.

Isn't the 6 ft rule only used when one is going to use the Liquid tite for bonding?

I have even heard that there are guys out there wiring pool lights in Liquidtight Non-Metallic conduit. Has anyone heard the same?

Article 680 includes permission to use LTFNMC for a pool light.