Is there a maximum length for tonearm wiring?

No, you won't lose part of the signal, because the cable impedance (at audio frequencies) will still be negligible compared to the load impedance (the input impedance of the preamp). But you do have to be careful about a couple of things.

If you have a moving magnet cartridge, you have to make sure that the total cable capacitance, plus the input capacitance of the preamp, are within the manufacturer's recommended range of capacitance for the cartridge. Otherwise you will lose frequency response flatness in the treble.

That is not a concern if you have a moving coil cartridge. But in both cases you should be sure to use a quality cable, which presumably would provide good shielding to minimize noise pickup.

Regards,
-- Al

What about MC cartridges which is what I use?

As I indicated above, load capacitance is normally insignicant for moving coil cartridges:

http://www.hagtech.com/loading.html

Regards,
-- Al

Oops. Make that "insignificant," of course, not "insignicant."

-- Al