Aeration companies suggest 24/7 operation as a default guideline to cover as many pond situations as possible. Aeration run times is a complicated topic due to the wide variability in ponds and type of aeration systems available from homemade to commercial units.
IMO running the aerator 24/7 causes more ware and tare on the compressor, more frequent maintenance / pump rebuilds, and compressors need to be replaced more frequently due to motor bearing failure.
Unless the aerator is too much or way over-sized you generally cannot over aerate a pond unless the air temps are in the high 90-100F. Then this makes the pond too warm and can harm numerous fish species including bass and BG. Amount of harm from excess water temps depends of several factors. Exceptionally strong circulation currents can re-suspend micro-clay sediments and keep the pond turbid to varying degrees. I have seen neutrally buoyant leaves moving in current from strong bottom aeration.
The general rule is to turn over the pond's entire water body a minimum of once a day. Many aerator companies will size the aerator to do that guideline. If you slightly or moderately over-size the aeration system then when you think, calculate, or measure the pond has been turned over at least once or twice in that day, then the aerator can be stopped until the next day. Generally for smaller ponds I try to over size the aerator so daily aeration is generally 2-8hrs.
I will look for a recent thread discussion in Aeration System questions where this topic was discussed at length. I found this one of several past threads that discuss aeration run times. NOTE - This thread does not discus and go into detail about water lifting volumes of diffusers. There is a past thread where that was discussed. Water lift rates of diffusers and the amount of air volume they receive determines how fast a pond will be turned over. There is about only one aeration company (Vertex) that has measured water lifting rates of their diffusers. All other companies with aeration diffusers are guessing or do not know lifting volumes.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=454091#Post454091Here is a thread this discusses lift rates. It gives a link to lift rates of Vertex diffusers. I found it by using google and typing: pond boss forum aeration water lift rates volume
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=492657Here is a bunch of reading homework about topics of pond aeration:
Diffuser location and Turnovers
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=489945How much is too much
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=496311Sizing for one acre
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=383205How many diffusers for 2.25ac?
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=252644Small pond system sizing discussion
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=252644Diffuser zone of influence
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=461601Aerator run times and sizing - TX
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=444639Water flow at the surface calculation formula
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=31894Diffuser selection
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=30911Aeration and influence on water temperature
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=30911