I would bet that a lot of issues with the unwanted “weeds” is stemming from some type of soil condition that if corrected would help alleviate their presence to an extent…… I would have to imagine that if you maintain a field in pure clover then the imbalance of C:N is going to cause issues in and of itself over time with undesirable stuff trying to fill that void….. I agree that some spraying is probably necessary in certain situations……Probably after initial establishment for sure…..I just don’t think this idea of maintaining huge stands of pure clover long term is the optimal way of managing……I wouldn’t be surprised if you don’t start running into chemical resistant weeds eventually