That depends entirely on who you define as a typical user. Since mankind has documented for several thousand years the use of marijuanna across a wide range of products and for a wide range of reasons perhaps examining who the typical users are historically gives insight?

Erik The Healer of ancient Rome used marijuanna extractions in ⅔ of his remedies. History records that the folks who lived back then reported that his prescriptions were effective. If those typical users noticed a shorter lifespan then likely they would have documented that too, but history shows the ancients thought it made life better.

Several thousand years passed in fact before the typical user really had any documented shortening of life from marijuanna. The phenomena of a shorter life from using marijuanna for the typical user began after the block buster US Federal government funded film documentary made in the 1930s called, “Reefer Madness” was released into American theaters. The film admits up front to being just a made up story but then portrays an incredibly fast journey from a good and wholesome lifestyle that degrades after smoking a joint into criminal insanity, rape, murder, hit and run assault, traffiking, racketeering, and irreversible mental illness forcing commitment. From a joint… typical, right?

So in the 1930s after scaring the living shit out of young mothers and fathers by playing upon their fears over their childrens future our “modern” generations decided that the previous three thousand years of human experience with marijuanna had come to the wrong conclusions, and that marijuanna was deadly to society at large. Oddly, for the typical user this indeed made it clear that in some cases marijuanna use substantially shortens life.

You see, for the first time in mankinds recorded history it became fashionable for governments to imprison or kill typical marijuanna users. The US filled prisons to brimming with typical marijuanna users. Statistically prison life is shorter, so in the US for typical users in states still imprisoning folks for it then lifespan is consistent with the lifespan of convicted murderers, rapists, and thieves who also serve time. In China and other places on the planet, typical users when caught have EXTREMELY short lifespans afterwards.

So the answer depends on who you determine is typical. The typical user before prohibition reported an enhanced and enjoyable life, not a shortened one. Typical modern and post prohibition users who got caught typical report a very different tale

Some also belives "Cannabis does not shorten a person’s life. Cannabis is medicine that improves one’s quality of life, and most likely helps you live longer."

what would you feel ?