Been there, done that!!!
When working at a Datsun dealer in 1973, the dealer owner installed 6 of that type of lift. 2 years later I was raising a 260Z when one side of the lift dropped to the floor. When I checked for the cause of the failure, I found that the lift had a very large screw on each side, that engaged with a large nut in the arm assembly. The Nut had stripped completely out, allowing the arms to drop. A few months later another lift failed in the same way, and at that point they were all removed and scraped. BTW, the Zcar sustained heavy damage to the Rt. side, leaving us with a very unhappy customer.
These lifts were used in a very busy Datsun dealership and probably were raised 20-40 times a day. they were not suitable for comercial use. But, for home use i would have no qualms about using one. It would last a lifetime in that application.
I would probably install some safety pins for my own piece of mind. ( MURPHY HATES ME !!!)