How important is it to have identical speaker cable length?

Anything more than about a 4" difference in length will smear the center image.

If you're ok with that, go for it.

And by '4"' I meant 400 feet.

@jerryg123.  

“Even if engineers have said the values are so minute the human ear can not differentiate the capacitance or inductance.”


Especially if engineers say that. Going by “engineers” quoting variables is the best way to end up with a poor sounding system.

And how about having bi-wired two lenghts, LF 1 meter shorter then HF? 

Perhaps you could think about making your room bigger to facilitate same length cables.

Now with over 40 years of analog design, I have come to the conclusion that the more you know, the more you realize how much you don't know.

Ala… Dunning-Kruger.
There are other practitioners of DK are also present here, so no offence intended towards you @spatialking … it is a wise observation and consistent with the DK findings.