My old piano teacher used to say this about when she usually assign:
Ballade no 3 - after 3+ chopin etudes at least one with arpeggios, a few nocturnes, a couple full length beethovens, or first year university studying piano.
Ballade no 1/2 - 4-5 etudes, a couple listz etudes, and a big enough hand. There are tons of technical difficulties with either of these pieces not describable with standard beethoven stuff or even chopin's own etude.
She told me dont worry about #4.