What I found last year, at least in the storms around salt lake, after the first 3-5 strikes of a storm you can count between shots and usually get a decent 10 second buffer. two storms I shot last year had 45-55 second spacing during the first half of the storm and 1:34-1:50 between during the second half of the storm, then it goes downhill and spaces out to over 5 minutes and the storm winds down. I went in last year to buy a 30d, but instead changed my mind when I held the nikon d200. Haven't had the chance of spending any time shooting a canon yet, would like to before I moved up to the d2 series or mark II