Flexible conduit limitations
I am rerouting wires in a condo. The original construction has every wire running through rigid conduit. It would be much easier for me to use flexible conduit for the reroutes. Are there any limitations to the length of a flex run? Can sections of rigid conduit be interspersed when it is convenient? Is steel flex better than aluminum flex? Please note that the wiring is such that all grounding is through the conduit, not through a separate ground wire. Thanks in advance for your input.