Our vet says 10-12 years, but I think the general opinion among Basset people is 12-14 years with some living longer than that. I've known three Bassets personally that passed on in their later years, Dudley - 11, Cleo - 12, and Rupert - estimated to be 14 or 15 (he was a rescue of uncertain age). Dudley and Cleo both died from cancer
and possibly would have lived a little while longer if they hadn't gotten sick.