Yes. You can have up to 5 supported recording devices on the one subscription, so long as they are all in the one household. For example, if you have 2 Topfields, 1 Humax and 2 Media Centres at home you can manage your recordings on all 5 of them with the one subscription.
What about multiple regions?
Because each account can only be set to 1 TV broadcast region you would not be able to have 1 recorder using Lismore channels and another recorder using Gold Coast channels both in the same account. In this case, even though both recorders may be in the 1 home, you would need 2 accounts, each with their own subscription.