Hi,

This is always a balancing act. Staying too long can lead to frustration and boredom. But, moving too quickly can end up making you frustrated as well because you can't play the more common chords cleanly and you sound terrible. 

I think you will find some chords will come along more easily than others. For these chords I would stay on a lesson until you can play a nice clean chord at a slow pace. Don't worry about speed. Think about finger placement and the structure of the chord. Just play the chord clean. An example of this would be C, E, D, Eminor. These are the easier chords to learn. Once you have them down, continued practice will help with your speed. And even though you may not be able to imagine it right now, in time with enough practice, chords will just "fall into place" under your fingers without much thought.

A can be challenging as can G, but F is downright evil for newbies.

What I would do in this case, is make it a point to go back to these trouble chords often and over time things will improve. We can always repeat our lessons and this in general will prove to be a good practice, especially once you start learning songs. It is always a good idea to play a song once every so often just to keep it in your memory and your fingers familiar with it.

It is important for us to remember that guitar is a very difficult instrument to learn to play. But by keeping the pressure off and the fun in, we will be more inclined to keep at it.

Best of luck!