Brice Helton's daddy, Cloid, was asked about this at a clinic a couple years ago. His answer was that in the regular season, you play as long as you can. Substitute as you can and get those kids some playing time. If it's playoffs, get the 45 point lead and end the game as quick as you can.
Assuming your team is deep enough, substituting is what you need to do. If you have three hosses (stars), start rotating them in and out. Maybe play only one (or none), depending on the depth of your bench. Anyway, your subs have been spending the season getting hit by your starters in practice, give them a chance to hit somebody else's kids at a game.
Sometimes, you don't have numbers and it's a mismatch. Finish the game at half, but not on chicken-salad stuff like kicking a field goal after calling a time out. And if it's close to the end of the game, it's bad form to run up that last TD to end it with a minute or two left.
And remember, be gracious in the blowout. Someday you may be on the other end of the scoreboard.