For me, the maximum range for my crossbow is 40 yards, just like it is for a regular bow in my hands. No matter how you slice and dice it, you're still shooting an arrow. One thing to remember is a crossbow bolt is lighter than a full size arrow. So in order to get the same penetration at a distance you need to use a heavier broadhead. I like 175 gr Slick-Tricks and due to the broadhead weight the arrow will begin to curve downward a lot more rapidly that a full size arrow that weighs them same amount fired from a regular bow. So I keep the distances for both at 40 yards.
If you want to try a farther shot, have at it. I'm letting them walk if they are over 40. I don't like chasing wounded game all over the county.