I have dino kale in my garden that is around 1.5 years old. Kales can be biennial or they may even perrennialise. They can look awful over summer and then perk up and put out lots of new growth when cool season comes around - but that will depend on your climate.

Cutting off seed stalks before they flower will encourage vegetative growth - keeping the plant producing leaves, but means no seeds for when it finally quits.