Yes available for more than 3 months deactivated vc, and dish tv is best in this type of offer. Suppose you are in new super family pack and got this offer, you will recharge 240*7=1680 and they will credit 240*12=2880 to your account, you may use total amount as general balance to add another channel/pack. Offer will not available for HD packs. But if you dont recharge additional amount to view HD, then you may use those offer amount, in that case due date will come closer i.e. if you have full on HD of rs 210, then your mly cost will be rs 440 and your vc will run 2880/440=7 months(almost).
But in Tata sky you will get no amount in your ac, you get only offer pack for certain period, that means you must have sufficient balance if you want to add another pack apart from recharged offer amount.