I am using the batter I would normally use for 1 x 12"

the 12" cake has a low bake  temp and requires 7 hours.

I will be dividing the batter between 2 x 8 " pans and will be baking them in the same oven at the same time at the same low temp . Would you still bake for 7 hours or reduce the time.? 

Up the temp and cut bake time by a lot. We have very limited info about your batter, but since you're familiar with this recipe, just bake until done. 

Thanks for that. I can't alter the temp as the key to the cake is the low slow bake. it is a very very old, heavy fruit cake recipe that cooked as instructed is the most moist cake. I have always cooked it for 7 hours in other  size tins up to 10 " size but never two at a time and never an 8" . When I do the same with other cake batters  the 8" pair seem to take longer than a 1 x 12'. Appreciate your advise.