My periods have always been a pain in the ass, lasting up to 3-4 weeks even with the dreaded Mirena coil thingy which I hate and want removed as soon as possible. Having said that I was on my period when I started and it ended after a few days. I was shocked as I was expecting it to last as long as usual. So I'm hoping LT was reduce them.
As for the being snappy, I found that on the first week of LT I was a bit of a monster. I was giving everyone a few home truths and I had the patience of a mad man. Maybe it was the carb/sugar/crap withdrawal or maybe it was PMT, not sure. I'm in my 3rd week now and you couldn't anger me, saying that my usual PMT symptoms should be starting soon so it will be interesting to see of they improve or worsen.