In my opinion cardio should be done year round, wether ur on or off gear, off season or pre contest. The frequency and intensity should vary though depending on ur present goals. For example off season i will only do 30 min cardio 2-3 times a week, pre contest i will do 30 min 5 times a week at the start of my diet and increase it to 7 times a week further on, some times near the end i can be doing 30 min 7 days with 2 xtra 30 min sessions before my last meal 2 days. But regardless of bein on or off a cycle i reccomend cardio, not just for keepin bf low but also helpin wi stamina n endurence wen liftin weights.