Pros: I found that if I wear my trays as soon as I finish eating dinner and keep them on until I wake up the next morning, I was able to fit into my new trays in two weeks without having to wear them all day! When I don't feel like wearing them, I have the freedom to take them off. You can ask your dentist if you can see what the last trays will look like! Great motivation! = )
Cons: You can't eat or drink with them on. If you lose them, you have use an older set of trays, pray that the next set will fit, or ask your dentist to order new trays for you.
I'm a 30 year old teacher, and I opted to use Invisalign because I didn't want to wear metal braces like some of my students do!