personally, i think the grace period is great. sometimes you might end up applying for a connection to be disconnected but only realize a while later that you needed that same number for some task. especially these days when your mobile number is connected to everything from bank account to aadhaar to income tax returns and what not.
even in case of postpaid, i am going to assume that the mobile operator might be able to reactivate your connection till the time the number is recycled. they would not allocate it to anyone else. but you might be able to get it for yourself.