A candle burn is affected by several factors including size and shape of vessel, wick, scent & temperature/draft in the room, etc.
To achieve the perfect burn, always allow your candle to completely liquefy across the top before blowing it out to avoid tunneling.
Before each burn, make sure your wick is trimmed to ¼”.
Don’t drop debris, like matches or wick trimmings, into the wax.
Don’t place your burning candle on sensitive or uneven surfaces.
Discontinue burning your candle when about 1/4” of wax remains.