Reply to Timecode and needle wear

over the last week i have noticed one side of my timecode vinyl dropping signal to the point the bmp fluctuates by about 2-3 bmp...

I play in clubs every weekend and normally have to weight the the needles heavy due to either

A) shit needles
B) Vibrations

What i would like to know is how do you know when it is time to change the needles using timecode? I know this may damage the vinyl more due to the fact they are being played constantly..... Where a normal vinyl maybe played every 2 - 3 sessions.

If it helps my needles are stanton 500 mkII.. I have had the decks for 6 months bought off ebay