As you grow in craft knowledge you will probably need fewer readers in order to get the same information from your feedback. Where before you may have needed the weight of opinion to convince you that a problem needed addressing, long experience will tell you almost immediately which reader concerns are important — either because they are outright mistakes, or because the resulting effect was not what you intended.
Too, as your craft knowledge grows, you may be able to get as much out of a one-on-one response as you do from a workshop. Part of this is that you won’t need to learn the basics, and part of it is that you will know how to ask focused, craft-based questions of your readers.
As always, the goal in doing so is never a defense of your work, but rather trying to determine whether and why an intended effect failed, or why a reader was brought up short by something you wrote. Unless the issue is one of editing (typos, syntax, grammar, etc.) the issues readers report are almost invariably sourced not at the location of the confusion, but somewhere else in the story. Learning how to identify the source of a problem from feedback about the effect of a problem is the goal, and being able to do so consistently is a practical definition of mastery.
When you have reached this level of expertise you will still need readers, but you will probably not need a formal or large workshop in order to gauge your own work.