Ok, I just finished an intermediate photographic course at the National College of Photography and the fact that each and every professional photographer said time and time again is set your ISO on 100 and leave it there - ALWAYS!!! 

So, I go with low ISO long exposure as well.  Play with your apperture though and see what the effect on any lights on your captures do.  You'll be surprised at the effect ;0)

The sole purpose in life is serving humanity.