A common question among language learners is how long will it take me to learn
<insert language>?, and the usual answer, for a native English speaker, is to refer to the FSI list, which divides languages into different categories of difficulty and gives good time estimates for serious students to go from 0 to B2/C1. That is all great and very useful in terms of helping a learner choose a language based on how much time they are willing to put in.
But another question that could be useful for language learners is to know how much time it takes to achieve each of the different CEFR levels. Specifically, what are the times to go from:
0 -> A1 A1 -> A2 A2 -> B1 B1 -> B2 B2 -> C1 C1 -> C2
We can probably expect the time to increase between each level. I assume any answer will be based on criteria similar to what FSI used, i.e., experience of training many students. For the sake of answering this question, use English as the L1 and Spanish as the L2.