Orthodontic retention is one of the most variable parts of orthodontic treatment amongst doctors. The concept is that the longer you can wear your retainer, the less likely your teeth are going to shift. Shifting of teeth has to do with a number of factors including the original position of the teeth, how the teeth were moved, how quickly they were moved, and the continuing pressures from the cheeks, tongue, lips, etc.It is generally a good idea to use retainers full-time for a period of time and then taper off to nightly wear only after braces. Another way to judge the amount of retainer time needed is how tight it feels when you put your retainers on. If the retainer feels tight, it means the teeth are trying to shift, and it would be prudent to use them longer. Hope that helps!