I agree - not too old at all. In fact, breeding at 5 successfully is better than breeding too young when you don't know what you have yet, or what the health will be. I won't take a puppy from a dam or sire less than 3 years old in my breed.
The one thing I wanted to add here however, is that these giant breeds are dying young, not old. Their lifespans are short but this should not be confused with a more accelerated aging process. A 5 year old Wolfhound is no different than a 5 year old Maltese in terms of age - it is just that we are losing these giants too young.
Six years old is the standard retirement age for breeding a dam - for a sire, the sky is the limit.