Mmmmm, say 50/50 success.
Late April, total pond failure - complete blowout of filtration system and massive health problems. Made a few shotgun improvements, but my DIY filtration system is more like DIW - Done It Wrong.
Because of April troubles, have changed my upkeep habits: change water religiously, no overfeeding, clean settlement tank (by hand - ack!) more often, not
too badly overstocked, keep use of chemical and meds to a bare minimum, etc.
Have to say that growth has been good this summer for the first time - some have grown 4-5 inches so far-and skin quality has improved. Feeding higher quality food as well. No health issues since April.
Intend to build a setup in the basement to overwinter the fish and allow me to make some filtration changes to the pond in spring. Large scale remodel of pond is doubtful at current house. Mike said for sales purposes we can pass our little pond off as a water feature as-is, but becomes an 8-foot toddler death trap if we did it up the way I would like it. So, will do it right "the first time" when we move. Until then, that is one high-maintenance puddle out there!