I Googled information from 3 pages of Motoro sites, as I have no knowledge of Motor's, None of the sites mentioned any knowledge of the longevity of Motoro's. Several sites provided additional reading material which may provide the information you're looking for.
Here is the most recommended reading material to further inhance your own knowlwdge. It may help. I'm not certain. But it's worth a try.
References and further reading:
Aqualog Freshwater Rays. Richard Ross & Frank Schafer (this is a reference book) Fishbase.com
Provided the right conditions, but I would say from what I see on the forums a large
percentage are lucky to survive a year or two, which is quite disheartening.......
Just imagine how many are sold in lfs that don't frequent forums and buy on impulse
and just watch them die becuase of lack of experience nor the ability to care for them
correctly.