I used to enjoy burning scented candles! Every evening I'd light at least one or two. I only used good quality candles. When we were packing up to move and when we took pictures down from the walls, I was horrified. The walls were so dirty; I never noticed until I saw the areas covered by pictures. It was residue from the candles. We had duvet blinds and when I lowered them, they looked striped, one part of the blinds were pale pink, others were gray. Again, the residue from candles.
The final thing that made me give up burning candles was because our house almost caught fire. It was Christmas Eve, our family left after dinner and my husband and I were relaxing. I fell asleep on the sofa; I was woken by my husband yelling "what's on fire?" I had a candle in a glass container sitting on an antique chest. The heat caused the glass to crack and the candle continued to burn through the crack onto the cabinet. The top of the cabinet was actually in flames! Fortunately, DH was fast, got the extinguisher and put the fire out.
So, now ir's only flameless candles in our house!