Do speaker wires have to be the same length for each speaker?

No!

There is a lot of debate on this subject.

For the most part I have maintained my speaker cable lengths to be equal,

There are several viewpoints.

I keep them as equal runs and as short as possible.

No they don't have to be. But I do used the same length cables to each stereo channel to keep the resistance/impedance the same.

Having the same length would help with resale as well.

Speed of electricity is 186,000 miles a second. A couple of feet doesn't mean much. But. I keep mine the same length because that is the way I am....