Hi and welcome to the forum

I'm no expert but I can only answer on the basis of my own experience.

You have said it yourself 'everyone learns at a different rate' so there is no definative answer.

What I would suggest is that you practice each lesson until you are comfortable playing the material contained in that lesson.

If you feel that you are not making enough progress, then it is quite acceptable to move on to the next lessons but make sure you come back to the problem and have another go later on until you have it under your belt.

I do not think you can not really pin it down any more than this.

The answer comes from practice. The more you practice the faster you will move forward. You should not over practice however. If your hands and fingers become tired then that is enough. Time for a break. It might be after 10 minutes or an hour. Whatever.

As you progress, you will discover your own limitations and know how long it might take you.

So. enjoy your playing. Take it forward step by step and have fun.

If you are ever having difficulties, just come and ask. Your tutor or any one else.

I wish you lots of success

Kind regards

Joe