Health
Mastiffs are a dog breed prone to hip and elbow dysplasia and degenerative joint problems as they grow older. Adult mastiffs, you might find, suffer from stiffness in the joints and sometimes even arthritis.
You must get a dog bed as soon as possible for your pup to minimize these problems as much as possible. Of course, adult mastiffs might already be suffering from such problems, which means that you need to focus on a dog bed that provides good support and pain relief to your dog.
Size
The Old English Mastiff is a huge dog. There is no doubt about that. Female mastiffs can weigh up to 200 pounds, while male mastiffs can carry almost 250 pounds of meat on them. This means that the size of the dog bed that you get will form one of your biggest considerations for such dog breeds.