The proof is in the pudding
I've had my hopes up on loads many times that shot well at 100 only to go back to the loading bench when I stretched them out. It's best to find the loads at longer range when possible, but that's often hard to do and I catch myself at 100 during development often. Consistent and exceptionally good at 100 usually weeds them out, but the true test are on past 100 if one needs more range from his equipment.