The longest living isotopes don't seem to be the atomic mass quoted (on wikipedia anyway):
{Element [Atomic mass]}
Dubnium [262] - Longest living isotope Db-268
Seaborgium [266] - Longest living isotope Sg-271
Bohrium [264] - Longest living isotope Bh-262
Hassium [269] - Longest living isotope Hs-269 (same) (my periodic table says: Hs [277])
Meitnerium [268] - Longest living isotope Mt-276
Darmstadtium [281] - Longest living isotope Ds-281 (same)
Roentgenium [272] - Longest living isotope Rg-280
As much as I trust wikipedia it could be wrong.