I know my strong colonies last season were allowing robbers in unchallenged - perhaps not a problem overall?
I did consider that these bees weren't aggressive enough (inspecting them was a pleasure), but even if they were more aggressive, having a wide open entrance made it too easy for robbers, and would require many more guard bees to be on duty and/or be recruiting worker bees to help deal with robbers (and detract from what they were already doing).
The other option was to leave them with a smaller entrance, which might mean a bit of congestion, but I thought on balance it was worth it for hives more easily defended and less likely to attract robbers from elsewhere with their potential varroa load and other diseases.
No right or wrong, just my thought process and decision.