I use Halo serving and lately I've been experminting with Angel Majesty serving. Both of these servings will last much longer than most of the factory servings. A few manufacturers have switched to Halo and some are using Angel Majesty.
The quality of your serving has much to do with how long it lasts. I got 25 shots from my factory servings on one of my high end bows, switched to Angel Majesty and it now has over 100 shots and isn't showing any wear. I didn't use rail lube on either serving. The bow has a camo string deck and it doesn't show any signs of wear. I'm sorry, but I don't have any idea what gut is.