Exactly how long can a tree live?

Thousands of years. The world’s 10 oldest living trees

There’s a group out west planting clones of redwoods and other ancient trees, some of which were over 4000 years old.

Some trees definitely have a life span. Others do not. I have a Bradford Pear tree in my front yard that is about 20 years old and the center of it is dead. Afraid it is coming out this year. Average is 15–25 for this species.

My white birches and weeping willows live on an average of 20 years. The birches break easily and the willows have shallow roots.

The group of big old guys on @jonsblond‘s link are worth having a look at for the other perspective.

I our town we have a hundred year old tree, but I believe some trees can live a few thousand years.

^^^See @jonsblond‘s link in first answer for accurate data.

According to this, some mango trees are still fruiting after 300 years. It could be that your tree will still be bearing fruit on 2/2/2222! :-o

There are trees on Meares Island in British Columbia that are more that 1,000 years old.

Bristle Cone Pines can live nearly 5000 years. The Monkey Puzzle trees in my yard have the capability to live up to 1000 years each.

How could they have such a long life span???

Lots of exercise, lots of fruits and veggies and very little stress, perhaps.