I had several online friends telling me that it was a huge waste of money to keep buying those stupid plug ins that plug into the electrical outlets and are supposed to last for a month. They never do. They last for maybe a week if your lucky and then you can't smell them anymore. So I bought an electric tart warmer and some wax melts. It's just a ceramic bowl that sits on a hot plate and keeps the wax tarts melted and that puts out the scent.
Here is one of the wax melts inside the ceramic tart warmer. it only took about 2 minutes before this was completely melted and started putting out a scent. I've had it plugged in all day and the smell has lasted all day. I turned it off when I went to bed and plugged it back in the next morning and the scent heated right back up. Each of these wax melts lasted about 50 hours and then I had to add another wax melt to the warmer.
I'll never go back to those plug ins and I highly recommend these now. it took me long enough. I had a bunch of friends telling me to get one of these and I finally just had to do it. So glad that I did.