You can never give your wife the look of bliss that comes across her face the moment she feels the first, warm, wet, goo of a strange cock splash across her lips...
It makes you sad when you see that disappointed look on your wife's face - the look she gets after a cock has delivered it's load and starts to shrink away. But you live to see that light in her eyes sparkle when a new cock is rammed through the glory hole for servicing.