The more the merrier, TBH.. I stopped at 78 natural I think, not sure of the exact number, could have been 75.. I don't make an exact science out of though. Push it as far as you can without hurting other main caps (agility, carrying mainly).. I've heard of some people actually going into the far 80's (natural) with speed alone.. That's when I think it would actually hurt your build from spending so much into one attribute, but those high ALG's (automatic level gains) are hard to turn down.. I'm sure there are others that would give you a hard figure to work with.. I just go with my gut

You don't have to follow everyone else's trend.. You may find that something better works, if you tinker with it.. Know what I mean?