It is super easy to over spice a pumpkin ale, I would rather err on the conservative side than to have a beer that will need to age forever because too much spice was added.
Here is the spice additions for a full boil batch of KingBrianI's Samhain Pumpkin ale.
1 t. cinnamon (5 min)
1/2 t. allspice (5 min)
1/2 t. ground ginger (5 min)
1/4 t. nutmeg (5 min)
1/4 t. clove (5 min)
Not a whole lot of spices there.