Does high PSI or low PSI affect the life of a tire?
Your best bet is to operate the tire in the pressure range on the tires. Check the air pressure regularly.     

Nominally if you are 180 lb or more then high number.  And 140 lb or less the low number.  In between then in between.  

Higher pressure maybe a longer life but still stay in the range.  If you weigh 140 lb then not worth a higher pressure for a harsher ride to maybe get a few more miles.

Race tires naturally have the shortest life.  

A soft rubber tire will wear faster but have better traction.  

A hard rubber tire will last longer but also poor traction and a harsh ride.   

And consider $ / mile.  You can buy a $50 tire that is probably not going to last twice as long as a $25 tire.