Speaker cable length

Hey y'all,

I'm thinking about changing the setup of my rig so the equipment rack is off to the side and nothing is between the speakers. However, that's going to entail a much longer set of speaker cables. Is there anything about speaker cable length I should be aware of? And and am I right in assuming that I need to keep both pairs of cables equal length?
I recently bought new speakers, new speaker cables and changed the speakers location. I now need one 5meter speaker cable and one 7 meter speaker cable. Was concerned the length and also length mismatch would be an issue. Unfounded worries, sounds great, soundstaging is terrific.
Amp=Conrad Johnson MF2250A .. speakers Magico A3 .. cables Morrow SP4.
It’s more important to keep your TT cable(s) short.

McIntosh guidance: for 18 awg: 4 ohm speakers:15 lf; 8 ohm 30 lf; 16 ohm 60 lf.

I finally made my new speaker cables (16 ohm speakers) two days ago, 16 lf each. I always keep speaker cables the same length. I needed to reach the further left side,

see 2nd photo here, system in background of ’cleaning’ photo


16lf gave me extra length at both ends: to leave them connected and pull my speakers forward, spin around, take the back off; and to pull the separate cabinet on the right side (with preamp and amp on it) forward, spin around.

I bought direct from Asia thru Wish, total 32lf for $215. delivered ($6.72/lf).

OFC Cat 8 S/FTP 22 ga, (8 strands equal 13 ga.) Pure Copper Spades, Pure Copper Connectors at Speakers.

My hands are a bit sore from stripping 64 strands, twisting, compressing the strands, attaching 8 spades with 2 set screws.

If your line magnetic 518 is this:  https://www.stereophile.com/content/line-magnetic-audio-lm-518ia-integrated-amplifier-specifications
Than you should not be worried about the cablelength...just keep it with low C. The nature of Tube Amps is of low to very low DF. As so, cable's resistance is insignificant. 
II use Canare 4S11 speaker cable.  Left speaker has an 18 foot cable, right speaker has a 15 foot cable.  Can’t hear any difference.  Won’t set you back more than $200.00 total.  The bested a pair of cables that were $1500.00 each. 
So I did the measurements just now. The right speaker is going to need 18 to 20 ft. The less speaker is going to need maybe 8 ft at most. Because of my triangle ratio with my listening position, a specials are about 11 ft apart and that accounts for the big discrepancy in the speaker cable length if I do move everything off to the side.