If it's only a dozen people or so, it's a pretty minor expense for them. The cost to the company is easily offset by the urban legends circulating among business travelers about knowing some guy that got free upgrades for life. That's a lot of persistent, viral PR for the quality of your customer service for very little outlay.
Looks like you already got your money's worth and then some so enjoy it. Hopefully it lasts for a long long time.