The optional rule is 20 dice or twice the sum of natural Attribute plus skill, whichever is higher. I would consider it worth it to max out a skill, though, since the bonus is a lot less conditional than many of the other social skill modifiers (contrast it with first impression, which gives a +2 bonus, but only within a narrow set of conditions). It is probably worth more to mundanes, though, because the adept improved ability power is cheap for social skills.