How Long Does It Take for the 'average' gap to fill?

Testing assumptions:

• Fade the open (9:30 am ET)
• Target = prior day close (i.e. gap fill)
• 1,000 shares of the SPY
• Oct, 2002 – October, 2011 (9 yrs)
• Min .10 cent gap
• Closed at 4 pm ET if gap not filled
• No commissions or slippage included