How Long Should my Invisalign Aligners Be out Per Day?

The recommendation is to wear the aligners for 22 hours a day. This allows approximately 2 hours for eating, brushing, flossing, and drinking during the day.
Teeth move when there is a constant pressure placed on them. There is some resorption of the bone on the pressure side, and formation of bone as the tooth moves. Unfortunately, the teeth aren't smart enough to know whether it is plastic or braces moving them. All they know is that there is some pressure on them.
Since conventional braces are attached to your teeth, you really don't have much of a choice about keeping the pressure, albeit light, on your teeth. With aligners, it really is your choice to wear them or not, but to keep treatment on time and on track, wear them as close to full-time as possible.

The more they are out of the mouth, the less they work. Long term stability might be compromised by having the forces started and stopped repeatedly. By all means take them out to eat and brush, but anything more than that may lead to disappointment. You have spent a fair amount of money on this service, so I would suggest getting the most out of it.

Jokes apart!
Invisalign is just another tool to move the teeth. Each aligner comes with a precise movement which has to take place and stabalize over 2 weeks period. If someone is taking out whole evening it will compromise the results. It might not be apparent during the treatment but could be in long term stability of the result.
If the prescribed movement is not achieved and stabillized in one aligner, the following aligner might not fit as well and might not track well with teh treatment.
Please compare it to the conventional braces. They are active all the time.
I recommend my patients to take them out for meals and brushing. It could take to half an hour or so but idea is for aligner to be in ALL the Time Possible.
Hopefully this helps.