Dropping file structure from photo archive

I'm trying to organise about twenty thousand photos i've taken over the last five years. They're sitting on three different backup drives. Basically, I want to organise the photos onto one drive, into yearly blocks, and drop month/day/batch folder structure.

It's taking too long to pull them all out manually - is there a more efficient way I could be doing this?

Providing all these were taken with a digital camera they should all retain the exif data. Using a program like iPhoto to manage them would then be a snap.

Import them into iPhoto and use the "smart folder" feature to organize the photos by years and months since all the photos already have date stamps in their meta data.

I do this as well, though I also use the facial recognition to tag all my kids to not only do all photos by date, but all photos by date with any of my kids too.

If you already use iPhoto to manage photos you can create a second iPhoto library to manipulate the photos you want to organize.

If you don't want to leave them in iPhoto you can use select all while in a smart folder and drag them into Finder folders if you prefer, though that makes another copy of them.