How much experience on average should a Sr. developer have to be competent with a framework or library? [closed]

Question

If you are a Senior developer with say 8+ years experience, how much time spent doing programming is reasonable for competency on average? Specifically working with some library or framework associated with the core language they have worked with. For example, 2 years of Spring or Hibernate for a java developer.

I understand that this is based on the complexity of the toolkit, framework or library, plus the competence of the individual developer, however, I'm sure there are reasonable ranges based on time with a language (hence the reference to Senior) that a Senior developer should be able to get competency and be productive.

The reason I ask the question is IT Managers should know this when writing requirements for a position and as a developer, I would like to have a better idea as to what criteria is involved for this type of experience = competency formula that has to exist. Even if it's a rule of thumb only.

What prompted this question is that I've found recruiters, who generally don't have a technical background, are trying to place technical people and they just look at technology buzzwords on a resume and how much experience for each the dev has. The hiring manager oftentimes doesn't have a technical background and does the same thing with the resume and uses his architect or other technical expert to screen the candidate to make sure the resume matches the person in the interview.

The problem here is the perception of "competency" in the mind of the hiring IT manager, whether or not the dev can really pick things up and run with it. They rely on some formula in their mind as to how much experience the dev has with a technology will work for what they want.