What happens if you change the Invisaligns 2-3 days late?

The timing isn't as precise as one may think, we don't look at the second hand of a clock to switch at the right moment.  The issues with timing are usually trying to switch too early/soon.  Longer is better, as a rule.The teeth won't move any more than with "perfect" timing, so it isn't beneficial, it just isn't BAD either.As long as you are following the protocol per directions, then you should be fine.The concerns that are most common are when Invisalign aligner trays break or get lost before the next aligner is due.

If you are late on changing your aligners, there is no harm. This will only mean that your treatment is now a couple days delayed, and the day you switch your aligners in the future will be different.

Not a problem at all.  Just extends treatment time.  However, going longer does not make up for not wearing 20-22 hours a day.