I don't think the learning ever stops, but it can vary on how long it takes you to reach a professional level, depending on your speciality, artistic skills, drive, technical understanding, problem solving skills, lots of factors.
you never really stop learning. in general, you can learn the basics of any 3d software package within a few days. you'll just need to practice nonstop in order to get yourself comfortable/experienced enough to land yourself a job.
We never stop learning. Technologies is always evolving and we have to learn new techniques everytimes. Learning a software is easy (2 weeks-1 month), but making good art of it can takes years of practices, depending on how you progress and how much effort you put on it.
Took me a year from scratch to get a job in the industry. But that was also a lot of luck, right place right time and networking. But yeah, like the rest says, you never stop learning. I do believe you can plan out what you need to learn and achieve to become "hirable" though.