Occasionally, we will talk with people who mourn the unexpected loss of a perennial that has been in their garden for ten years or more. I have always 
wanted to ask these people if they had the secret for their own immortality available so that I could buy it—rent it—lease it.
We humans are very quick to accept or even embrace blame and responsibility when a plant dies. Usually, despite our careful care and feeding, plants reach the natural end of their life cycle and pass on. It is not our fault or responsibility, however. And it isn’t necessary to feel badly or God forbid, behave as though we failed the plant. Some people feel guilty.
Some perennials are notoriously short-lived—Shasta daises, fleabane, flax, soapwort and gaillardia are a few examples. Genetically, they are destined for 2-3 years of life. Sometimes, of course, they persist for many years. We have heard many gardeners report remarkable examples of longevity. Count yourself a lucky person, if this is your experience. It doesn’t happen often. These are plants that, for whatever reason, can be reasonably expected to thrive for a few brief seasons and then to leave the garden. And this is why people are bewildered when a plant that has seemingly been content, suddenly, one spring, never appears.
(Passing along a rather poorly-kept secret: sometimes these perennials reseed and only pretend to return faithfully year after year. In reality, they are growing new plants yearly and thus, fooling you into thinking you have one of the persistent ones. What you really have are healthy teenage seedlings.)
Most perennials, on the other hand, are very sturdy and long-lived. Peonies are handed down through generations of families, hosta seem to live forever, daylilies can and do populate a neighborhood when a generous gardener shares divisions and bleeding hearts are faithful springtime residents of the shade garden. These, along with many others, are perennials that, when planted in the correct place, with the correct food, water and light requirements met, will be stalwart for even the newest gardener. And reasonably, you can expect them to live for many seasons, growing larger and stronger. So much so, that eventually, you will divide them, of necessity.
The factors that influence longevity are not only genetic. Environmental factors, such as light, water and nutrition, will obviously be important. External factors such as harsh weather, rowdy animals, insects or human abuse will count for a lot (just try rooting a severed peony stem after is has broken off during a violent summer rainstorm). 
And remember that plants are vulnerable to disease and old age, just as we are.
It helps us to look at the unintended gifts that gardeners receive from nature (the generous reproduction of lily bulbs and daffodils, for example), rather than to focus on the short-lived beauties. We continue to grow and sometimes, replace the odd Shasta daisy, in our gardens. And be glad we have them. The garden simply would not be the same if they were to never return.