I suppose it slows you down a bit if you're on a roll...maybe trying to raze cities only one at a time is a better approach.
Another strategy to think about instead of razing cities is to puppet them and maybe sell/give them to some other civ...a civ who really isn't a threat to you and who might also cause some problems for the civ you took the city from.
Sometimes I've found that if you raze a city and leave an inviting gap in the terrain some civ ...maybe the one you took it from ...will "reflexively" send over a settler...
Though with happiness not as much of an issue in G&K, I find just puppeting them and forgetting about them...except for the choice ones... seems to be an easy enough strategy.. though I play at the King level...maybe at the higher levels, even that is a game-losing luxury you can't afford to indulge....