When in the dreary hour of decline

[adonais]

Do you happen to know/recall who said that a good sonnet couldn't be written in less than a month, or something like that?

I don't recall that, but I doubt it was Keats, considering his 15-minute sonneteering duel with Leigh Hunt in 1816, wherein he wrote the sonnet "On the Grasshopper and the Cricket".  ;D