I Have One Week Invisalign Trays Prescribed for 20 Weeks. Everyone on the Posts Seem to Say Theirs Are 2 Week Trays?

There is certainly a range of how long the trays get worn by that seems on the short side. I would verify with your doctor that this is the protocol they want you to stick too.

Do you have a lot of open space available in your teeth? If so, your dentist may be anticipating your teeth to move more freely and quickly because there is space to move. So cutting down the time to one week could work quite well! Good luck!

I'm not sure why this was recommended by your dentist. You should ask them the next time you are in for your Invisalign visit. 

The only advantage that I could think of is that the trays won't accumulate as much odor or discoloration because they are being switched so frequently.