diff -r 4af84eb4246d product.py
--- a/trytond/trytond/modules/stock_supply_production/product.py	Tue Feb 17 21:08:47 2015 +0100
+++ b/trytond/trytond/modules/stock_supply_production/product.py	Wed Apr 15 17:57:32 2015 +0200
@@ -10,8 +10,10 @@
 class Product:
     __name__ = 'product.product'
 
-    def get_supply_period(self):
-        'Return the supply period for the product'
+    @classmethod
+    def get_supply_periods(cls, products):
+        'Return the supply period for each product'
         pool = Pool()
         Configuration = pool.get('production.configuration')
-        return int(Configuration(1).supply_period or 0)
+        supply_period = int(Configuration(1).supply_period or 0)
+        return dict((p, supply_period) for p in products)
diff -r 4af84eb4246d production.py
--- a/trytond/trytond/modules/stock_supply_production/production.py	Tue Feb 17 21:08:47 2015 +0100
+++ b/trytond/trytond/modules/stock_supply_production/production.py	Wed Apr 15 17:57:32 2015 +0200
@@ -87,8 +87,8 @@
                     product_ids, with_childs=True)
 
             # order product by supply period
-            products_period = sorted((p.get_supply_period(), p)
-                for p in sub_products)
+            products_period = sorted((sp, p) for p, sp
+                in Product.get_supply_periods(sub_products).iteritems())
 
             for warehouse in warehouses:
                 quantities = dict((x, pbl.pop((warehouse.id, x), 0))