There has to be otherwise the engine would both run hot and/or show physical wear symptoms.
When you shut them down, are you running/burning the fuel out, or just letting it idle and then shutting them off?
There is a LOT of windage around the bearing with the engine running and post-shutdown you're only going to see a t-tiny film sitting on the face of the bearing. If you were to let the engine sit, then you should see a very small amount puddle to the bottom of the bearing, below the crank counterweight. This takes a while though.
If you're not exploding bearings or have any signs of wear or other outwardly nasty symptoms, don't worry about it.