Am I correct on this?

Question

A type stars would live the longest out of the main sequence stars of types A, G, O, and K correct? I'm pretty sure Red Dwarfs live the longest.

Answer 1

It goes OBAFGKML.  O is the biggest and shortest-lived; M and L are dwarf stars, small, cool, and have the longest lives.

Answer 2

The hotter the star, the shorter it lives.  Its too bad the stellar types are in alphabetical order.  In order (hottest to coolest) on the HR diagram:

O

B

A

F

G

K

M

I use "Oh, Be A Fine Girl Kiss Me" to remember the order.

So A type stars are hotter (generally) and therefore have shorter lives (generally) than F, G, K, or M stars.