I've only had a diffuser for a few months and this is the third company I've bought the oils from. The first one was just one bottle of lavender and for some reason it felt like my mouth and nose was coated in plastic when I was using it and it didn't have much scent. The second time I ordered a set. It was better and the scents are nicer, but I had to use 7 or 8 drops to smell it from the diffuser. But this one is great. These are in a very nice box that pulls out and the bottles are in there own little section. Each bottle was sealed, but you could still smell the aromas. The first time I used the lemon gras and put in four drops. WOW. Almost blew us out of the room. These oils will last. They have some power. That's what I was looking for. After the first try I cut back to 2 drops in the diffuser and it was perfect. I will be buying more of this brand. It's well worth the price and I only have to use half the amount as the other oils.