It all depends on how they are treated, they can last a few years, but they can break if dropped on a hard surface. My personal molds are already more than 5 years old.
You can recycle old plastic lures or you can purchase new plastisol.
As with any process it takes practice. If you can operate a Microwave and use a syringe it is not difficult at all. Just ensure you adhere to the instructions provided and follow all safety protocols.
Depends on the temperature when the lure was injected, ussually around 2 minutes, but bigger lures take a bit longer.
As long as the master is not too intricate with small appendages or undercuts, anything is possible. Contact me directly to see wether a mold is possible.