Thanks for the link! It's the first time I've seen replacement intervals for the electrodes, something I've wondered about for a long time! 600 hours doesn't sound too horrible for street lighting, I'd roughly guess an average replacement interval of three times a year. With regular carbons (175 hrs.) it'd be closer to monthly.

In all fairness, in my personal experience those pre-WWI arc lamps are nothing to yearn for though. They emit a horribly bluish, flickering light and make loud buzzing noises. I'd say the colour temperature is close to a neutral white mercury vapour lamp. They seem to have been phased out quite early. I've seen pictures of Vienna railway stations built in 1898 and all the original arc lamps had been replaced by incandescent fittings by the mid-1920. They didn't only remove the guts of the arc lamps and put incandescent bulbs into the original fittings, they removed everything and replaced the fittings with new ones, plain metal shades and pickle-jar style glass covers over the lamps.

This painting shows the original arc lamps:
Another picture:

The 1920s replacements:

After WWII, the stations were soon converted to fluorescent lighting. Today they have a combination of replica arc fittings with discharge lamps and fluorescent battens, currently under conversion to LED.