I would let the spawning finish because many eggs will naturally be infertile, especially for inexperienced fish, and also because you WILL have a die off. If you stop them early, you won't get as many strong, healthy eggs and fry, so the die off will leave you with even fewer good, strong fry to choose from. Your best bet is to cull out the weak, small, deformed etc fry yourself.
Tpocicat is right, this is all opinion and asking everyone what they think about breeding practices likely won't get your any closer to a hard answer.