even a simple rotation like corn -> soybeans can aid some bacteria recover, thus a better soil lifespan (high productive areas with proper management (beyond rotation, like some rest and proper fertilization can last ~ 120 years being abused all the year long)

probably hundreds of years if erosion wasn't a thing [0]

but "regenerating" as the OP types is probably about actively managing land recover while planting some sugarcane in between the process. now. if the harvest will be profitable for making biofuel is probably another talk

[0] just a guess