Do three component cables have to be the exact same length? I want to use two 25' RG6 cables with F connectors already attached and one 30' RG6 with F connectors attached. I'll then use F to RCA adaptors on the ends. Will this work? Thanks
Assuming all three cables are exactly the same manufacture, the signal will take longer to go through the 30' cable. Assuming a Velocity of Propagation of 82 (typical for RG6) the delay per foot is 1.24176461705966e-9. Will a less than10 nanosecond delay be enough to be visible? Probably not. FWIW for about $10 you can get a proper Component cable from Monoprice.
The propagation delay, as olyteddy states, works out to about 1.25 ns per foot. There's a broadcast-quality standard for this sort of thing, which I cannot recall, but I'm sure that it's more tolerant than the 6 ns involved here. Bear in mind that this assumes all cables have the same dielectric; if they don't, the propagation delay will be smaller, or larger, as the case may be.
On the CCS versus solid copper issue: it may matter whether your cables are all of the same composition, because a CCS cable is going to exhibit a bit higher attenuation and you don't want attenuation to be significantly different on different runs. Most CATV coax is CCS--you can usually tell just by examining the end.
I don't know the Monoprice products but it's pretty unusual even for Chinese component video cables to be CCS. Ours are all solid copper.