If you look at the List of Our Octopuses, you'll see that all don't live out their full lifespans. While some of these die early due to human error, others just seems to pass away earlier than others, just like humans. So Tom, if you get 10 months, you'll be doing quite well.
And nini, I don't think you can say that a bimac is better than a briareus or vice versa. They are different but both can be nice to keep. Bimacs were more available, which is why our members have kept so many.