Neither of the rums post their ages at all - gives them a degree of latitude that I'm sure they enjoy....
The McDowells Celebration is one of the biggest selling rums in the world - selling by the swimming pool load in India. The Oronoco, despite proudly displaying it's Brazilian origins with a map on the bottle mostly comprises rum from Venezuela, from the Pampero Distillery actually.
A lot of distillers are increasingly avoiding putting ages on the bottles, some because it allows them to continually modify the blend, some, more proudly, because they don't believe in supporting the 'more age=better rum' argument. As long as you enjoy it, it really doesn't matter.
That said, if you enjoy the McDowells and you're not on a Goa beach, you might want to try some better rum for even greater pleasure!