Quit and never come back is very unlikely for me, maybe for one of the reasons already stated like losing your character for reasons beyond my control. My character is very poor and don't have many gear or jobs lvled up but the sense of losing it is not very pleasant.

However i do take very long breaks, i played a bit during HW launch and came back only after 3.4. My subscription is ending next month and i'll probably just come back after 3~4 patches after 4.0 if they keep the same schedule as 2.x/3.x.