Here's Ben's advice on the topic: http://www.poolsolutions.com/tips/tip06.html
Bottom line is that he recommends evening chlorination to save on chlorine costs. I wouldn't sacrifice maintaining proper chlorine levels at the altar of saving a few dollars (e.g. your scenario of finding borderline chlorine levels at a mid-morning test) , but with daily testing and a little planning you should be able to chlorinate almost exclusively after dark.
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