This 7 day candle is used to bring protection against evil and harm.   A traditional 7 day candle should be allowed to burn for 7 days straight, but if that is not possible, snuff out the candle (never blow out candles as they blow out your intentions) and when you are ready to relight it - refocus on your intentions and light it and allow it to burn for as long as you can.  Be sure you burn it for 7 consecutive days