ah yes, cracking 1:50, when in May is your race? Where are you pacing your current long runs?
I'm doing the Historic Half Marathon in Fredericksburg on 5/20. As for the pacing on my longer runs, I'm not too good about that. I generally start out too fast and take a while to settle into a steady pace I can hold for a while. I use an app called Cardiotrainer on my smartphone to give me my splits. I'm hoping to average around 8:15/mile for the half, which would get me under 1:50. As long as the heat isn't too bad, I should be able to hold that pace.