For me, it's 32 skills.

2 cross hotbars worth of skills. Any more than that and it becomes more difficult and time consuming to juggle bars to get to the commands you want. I believe that all jobs should be streamlined to hit a nice total of about 28 job/class skills with another 4 cross role skills.

Pet classes make it more difficult since you really need closer to 48 total skill slots to properly manage Pet Skills in addition to your own, and that's too much controller manipulation for me personally. Maybe one day I will figure out this 3rd cross hotbar arrangement, but for now I am comfortable with 32 commands on 2 cross hotbars.