Every case is different and it depends on the size of the abuse, of course. It's not the same a guy who has been completing free offers without VPN and then used VPN a bit, with a guy who has get 20.000 tokens using VPN.
Everyone ABUSING VPN and getting caught is getting a ban. Obtaining a couple of tokens / day with VPN during a week is not abusing, although the user in this case would get his tokens deducted and receive a warning.
Of course we are talking about using VPN but legally completing offers / watching videos. Cheating gets an instant ban no matter how small was the offer.