I think many of the guys stayed on for years and years because JE is all that they have. Most of them joined the company when they are 11 and 12. Their whole adolescene is with the company, their closest friends, their formative years. Many of them gave up school in order to make time for shows and concerts, I don't think it is easy for them to leave the company unless they have something solid to fall back on. Moreover, they have been in the industry for so long and worked so hard to rise to the top, leaving the company would be years of hard work down the drain.
Aiba's craziness is just a fraction of the K8 members, when the K8 members host their own variety shows, they are hilarious in the things they do and say. I have a favourite member in the group, Shibutani Subaru, but I like every single one of the members in K8. I am not sure what type of music you like, but some of my favourite songs from K8 are
Osaka Romanesque ,
Osaka Rainy Blues ,
Mugendai and
Eden
They have some rockish and enka-ish songs as well, but those that I listed are more mid tempo and easier to digest. Actually K8 is known for having some really fun songs with Osaka flavour and enka (traditional) sounding songs.