Hi NHdad,
Latex is certainly a very durable material but I would also keep in mind that there are also other factors involved in the durability or useful life of a mattress outside of just the material itself (see post #4 here) so while it’s not realistic to expect every latex mattress to last 40 years for any specific person and it will depend on the specifics of the mattress, as a group they will certainly be more durable than any other foam materials.
For those who prefer latex over other materials (or some type of latex hybrid) there is really nothing else that will do 
Phoenix