There are many passages in the bible that speak of lamps, most of them in relation to God's people. People are constantly changing, just like the lamps have over the years. They look differently, speak differently and live differently, but one things remains unchanged; they are still fueled by the same oil, Holy Spirit.
To this day, you must use clean, fresh oil in your lamp. Using clean fresh oil ensures that the light is strong and constant. Using unclean, or old oil in your lamp has dual affects.
1. Firstly, there will be an odour. If you continue to use old oil in your lamp, there is every chance the vapour it is emitting will cause everyone to vacate the room. We must keep a fresh infilling of God's Holy Spirit if others are to be drawn to His light. We cannot live on someone elses annointing, a past annointing in or even yesterday's a annointing. The fresh oil comes from spending time daily in the presence of God.
2. Secondly, the flame will smoke and soot. If you continue to use old oil in your lamp, the soot and impurities from the flame will dull the light being omitted by the flame. On newer lamps, it will even soot up the glass completely. Clean oil is essential to burning a clean bright flame.
When was the last time you allowed God to renew the oil in your lamp?