What record do we have of the length of supernovas? recently I heard an astronomer on the radio claim that the supernova we have observed in our own galaxy lasted about 6 months, while in distant galaxies they last about 7-8 months, due to relativity and the expanding universe. He didn't give any references. Just to be clear, I don't mean to imply that he implied the actual duration was different, but that it only appeared different because of expansion. 

I've found records of supernova, but only 1 mentioned how long it lasted, the first recorded one was said to last 8 months according to wikipedia. 
Can someone point me to a list that contains both the location and duration of supernova's .
I would expect that the further away a supernova is, the "longer" we observe it will be active because of an increased red shift.  Objects in the universe that are further away are generally going away from us faster than objects that are close, hence the increased red shift.  This increase in time due to redshift is very similar to the Doppler effect, where a siren is high pitched (and faster) when approaching you (e.g. blue shift with light), and low pitched (and slower) when going away from you (e.g. red shift with light).  The faster the siren is moving away, the more the effect (both lower pitch and longer time) will be increased, likewise with light.

Here are some sources that may help with what you are looking for (although I haven't been able to find a list exactly like you are looking for):

http://www.wolframalpha.com/input/?i=supernova

http://en.wikipedia.org/wiki/Supernova#Light_curves

http://en.wikipedia.org/wiki/Cosmic_distance_ladder#Type_Ia_light_curves

http://curious.astro.cornell.edu/question.php?number=49