My understanding is that generally they average around 10 to 12 years, but some can liver longer and others have a much shorter life span.
My Diva was over 13 years when she passed. Monty was just 8 years and one week and he dropped dead suddenly of a suspected heart attack.
I now have Dora is she is just over 2 years and I hope to have her for a long time, but who knows.
I have really only had Diva as a senior and she was awesome in her older age. Until she partially ruptured her cruciate at age 11.5 (I chose not to have surgery performed) she was very active - even when she was mobile again she was still pretty active. It wasn't until the final 9 to 10 months of her life that she really slowed down when a heart issue became apparent. The seniros are pretty special - they look at you with such wisdom and are so content. That didn't mean however that Diva wasn't still naughty in her older years, because she could be
Just make the most of everyday you have them - I try to remember this myself when young Dora is being a brat and totally misbehaving or destroying or stealing something :rolleyes: