Removed depedency of System.Net.CookieCollection and Cookies, and used my own struct Cookie class for cookie text processing for quicker processing. Created SessionLength metric class. Modified code to use TryValue for retreving Dictionary values. Due to frequent misses of values it slowed down the metric computation and due to frequent index misses it slowed down cookie computation. Hourly aggregates from 6/06/2013 - 06/18/2013 of a 813kb log file now takes 24 seconds for metric computation. Which is a 80% decrease in how much time it took when it was 1:53.