Disappearance of a Fool

Since I am interested in the role of the fool in King Lear, I am naturally curious about the same fool's disappearance from the play.  Throughout the first three acts, the fool is fairly present, speaking wisely and honestly to the King and providing valuable social commentary.  I rather enjoy this character and then *poof* he's gone.  The fool's last appearance is in Act 3, Scene 6, which leaves two acts without this intriguing character.  Why?  I have begun researching this mystery and have come across some interesting theories.

Schmoop (similar to Sparknotes) speculates:

"Some literary critics even speculate that the Fool and Cordelia were played by the same actor. They never appear onstage together, so some scholars hypothesized that the part was double cast, and that the Fool had to disappear when Cordelia came back into the play."

This is an interesting speculation.  Cordelia and the fool actually have a fair amount in common.  They are both wise, intelligent with their words and speech, and loyal to the king.  These are rare traits among the other characters (at least lumped altogether).  Additionally, in Act 5, Lear laments, "And my poor fool is hanged."  "Fool" here could be a pet name for Cordelia, or could refer to the fool himself who may have also been hanged.  This is not clear in the text.  Maybe they are essentially one in the same in the eyes of Shakespeare.

Another speculation (taken from Gradesaver.com) is that the fool disappears when King Lear realizes that he himself is the true fool.  He has squandered the love of Cordelia and Kent (the two truly loyal to him) and realized the wicked heart of Goneril and Reagan (not to mention their husbands).  As he realizes this foolishness, Lear descends into madness and takes on the role of the fool himself.  In this sense, the fool does not necessarily disappear, but rather takes on a new role manifested in a different character.

I like both of these ideas.  It is even possible that both are true.  Unfortunately, I cannot ask Shakespeare himself the reasoning behind this decision.  However, I think this will be my question for Turner when he visits this week.  I am interested to hear why he thinks the character of the fool disappears from King Lear.