Oh yes. I don't try to redo them though. I find something new to say with them. Shirley digitized is a good example of this. She was a black and white painting, with little detail. I shot a photo of her and added a bunch of stuff, messed with her eyes and voila! I have one old painting (acrylic) of a living room scene, which I shot and is stamped (made into a brush) or used prominently in several digital pieces, including Shirley digitized. Recycling is a property of digital art and to me it sort of reflects the way the mind works, particularly the memory.
Well, when any artist attains a modest amount of skill with a medium and uses it for self-expression and experimentation, we get to peek into their mind. People are dazzled by skill, but it's the aspects of mind and personality that come through that truly make a piece of art, art.
That's cool. I learn something technical with almost every piece I do too. As for the emotional or intellectual side of old work, I think as you get older and perhaps have children and/or accomplishments and failures, you become sort of nostalgic. For me, this isn't (I hope) simply longing for the past and youth, but rather an attempt to understand (or affirm) who I am now, through who I was then.