i notice some older mercury vapor lights in my neighborhood flicker on and off many times,before a stable arc is struck,besides old age what causes this?

From what I know, as the lamp ages, the electrodes become depleted of emitter and cause an unstable arc when first started. Sometimes, if there is excessive sputter on the quartz walls, the sputtered metals will also conduct current causing the arc to jump around in the arc tube at first. Also, the electrodes might start to glow brightly in incandescence (sort of like fluorescent filaments when old).

just a thought if a mercury vapor lamp has very high hours on it does it reach full tempature,and pressure.

no.

From what I have tested, it seems that MV still does reach full pressure and temperature, as they still draw the same wattage.....and they have to reach full pressure to draw full wattage. If anything, they may even run hotter since the arc tube blackens and absorbs some of the energy as heat.

Don,you are absolutely right,i've observed this in one of my regent lamps that was accidently connected to mains,the current severly darkened the arctube but the lamp was still functional,the blackened area's glow Red Hot when the lamp is shut off,so your conclusion is correct,Thanks!