I have an APW3++ running a single 741 and an APW5++ running two 741s. I just took my laser temperature reader and measured the wires.
They were all between 85-90F with an air temperature of 65F. That temp for wires is not going to be a problem. The insulation on the wires will start to go at about 180F but if the wires get that hot, the PSU would probably fail first
I think the wires are 18AWG (or 16) and can carry a max of 10A each continuously so we would probably have to pull a lot more current through for it to be a problem.