There are several different connection types used for PEX connections depending on the manufacturer and none of those standard connections are like the "Sharkbite" ones. There are a couple varieties of crimp connections and at least one type that uses an expansion tool to briefly expand the PEX to fit over the connection and the PEX then contracts solidly over it. All have been in use for a number of years now with no apparent issues.
On the subject of the "Sharkbite" style connectors, they are essentially the same as the push lock connectors that have been used in both industrial automation pneumatics as well as in heavy truck air brake systems for many years with no apparent issues there either. As long as they are made with proper QC and proper material selection, there is no reason that they should not outlast the life of the tubing itself.
On the tubing life subject, I will note that in hard water areas copper pipe / tube will have a much shorter life span than PEX.