If all the trees in your environment appear happy, healthy and proper - with no possible threat to your safety, home, or property - then perhaps you should neglect the when and where tree failure question and look for something else in the world to worry about.
However, he safety and health of tall and leaning trees of your own, or your neighbors, can best be monitored by you yourself who have the opportunity to observe and inspect routinely.
Here are a few things you want to watch for to detect root rot: mushroom or fungus growth at or around the base of the trees. Clear vegetation and leaves from this area and keep it dry from sprinklers. Also, sparse leaf or needle growth, and yellowish color instead of dark natural color (Yellow needled pines most likely are the late stages of a deadly beetle infestation. Around March 1st is the optimum time for spraying pines and cedars to kill beetles.)
For leaning trees, try to mark the angle of its lean and record the rate of any increase in angle. This can easily be done by standing behind a fence post or porch support post and draw a straight line using a business or credit card at the same angle of the trees trunk pitch beyond. Date your mark.
Sometimes you will think a leaning tree is leaning more than it did before, but aren't sure. Look high and look low. High if there are straighter more dominant trees. You will see open sky where the trees used to touch. Down at the base, inspect behind the lean for root ball lifting or cracks in the dirt. You can also stomp your feet in this area for a muffled drum sound if there are not too many leaves.
These routines should be practiced on all large trees of concern after every Santa Ana high wind storm.
If a leaning tree's root ball is not longer tight in the ground due to the rocking of high winds, the tree might be saved by topping or heavier than normal reduction trimming. But if a tree has root rot, delaying its removal is not a good idea, especially in the rainy season.
If you identify a dangerous or threatening tree belonging to your neighbor or city, and inform them by certified mail of such, then the rule of "responsible cogency" applies and the act of nature rule no longer relieves the owner of their responsibility to prevent their tree from damaging your property.
However if one mails such a letter, one should be prepared to see that tree removed. If that is your intention and no action is taken, you may want to try sending a copy of the letter to the insurance carrier.
Alternately, you can call an expert for an opinion. Or ask your neighbor to contact one. Safety should be the primary concern of all good neighbors. If you have questions, give me a call.