Using my new log analysis script, to analyze a half day's worth of logs...
(146000 lines, 15M)

Sampling every n lines, the times were as follows

N		Time (seconds)
500		  4.5
200		  5.3
100		  6.4
 50		  8.7
 20		 15.3
 10		 26.2
  5		 48.0
  2		112.7
  1		219.7