I afk'd 99 att / 99 str / 90+ defense and 99 range there.
I have 77 million NMZ credits and that's what I have left over from buying the absorbs / ovl's too

Now I don't afk it and I just do slayer when I have time. All the nubs around me love to talk shit about my slayer level compared to my combat level. haha
It does make a good conversation starter. If you are able to afk at work or something I'd definitely do it, but if you're going to sit there and watch your screen / movies next to it I'd say slayer is pretty afk'able for that.