Both sets of bocks are exactly the same quality wise. What you get with the PJ+ are nicer bindings and calf cuffs. If you can afford the + I would say it is worth it. They won't last longer but your bocking experience will be improved.
The best way to make them last is to look after them. Use silicone spray on the bindings often, make tire socks or get some hoofies, protect the springs and just look after them. Springs do wear down and will need to be replaced. The time they will last depends on how much you use them and your technique but lets say something around 8-12 months is about normal.
