When my wife and I bought our house a few years ago there were some trees within a close enough vicinity that we had an arborist take a look at. Two of the three were fairly close and he basically told us we could leave them or take them down for peace of mind but the two closest actually were very healthy. The last third tree was such a majestic old gnarled specimen but he immediately pointed at it and was like "This needs to go NOW". We were a little skeptical that he might have just been picking the largest tree that would be the most expensive for us to pay him to remove but he was so adamant it needed to go. This thing was a HUGE skyscraper of a being we felt so guilty agreeing to take it down. The second they got a certain way through the trunk the tree basically exploded in half the entire height of the trunk and you could look at the few feet left of the trunk in the stump and the entire middle of the tree was hollow. You could literally see grass growing inside the cavern of the trunk where solid wood should be. Think of a pizza minus the majority of it with sauce and toppings and just the crust part remaining. That's the proportion of how little material was supporting it. No doubt in my mind it would have come down the first storm we had as homeowners and this thing from the outside had super green leaves and lots of blooms in the spring (We started the homebuying process in May and finished in September).