What's wrong with 6-7 ft tonearm wires?

The level of the signal from the cartridge is very low, using this length of cable will have undesirable consequences if you are looking for the best possible sound.

I had to move (2) of my turntables a little further away from my systen and went from a 1 meter to a 2 meter (6 1/2 feet) and heard NO difference in sound quality. I think it depends on the quality of the cable. I use Cardas on both of these 2 meter setups with excellent results.

Would the capacitance be too great in phono cables this long?

It depends on the cartridge type, the parameters of the particular cartridge, the capacitance per unit length of the particular cable, and ability of the phono stage to gracefully handle ultrasonic resonant peaks.

If the cartridge is a low output moving coil, the response of the cartridge itself within the audible spectrum will be pretty much insensitive to load capacitance. However, greater load capacitance will increase the amplitude and lower the frequency of an ultrasonic resonant peak, which may result in phono stage distortion products that fall within the audible spectrum. See the excellent post by Jonathan Carr (JCarr) dated 8/14/10 in this thread:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1281468389

If it is a moving magnet cartridge, load capacitance that deviates significantly from the manufacturer's recommendation will cause frequency response in the upper treble to be non-flat. It is possible to have too little capacitance as well as too much.

Assuming you are referring to an lomc, if you choose a very low capacitance cable (e.g., 10 to 20 pf per foot), that also has quality shielding (to minimize noise pickup), fwiw my suspicion is that you'll be ok.

Regards,
-- Al

Should be no problem especially if going balanced into the DM10.
Great pre & phono section - I run everything balanced on mine.

Its ok 1 meter is better as its very low level signal.