As per several High Court and Supreme Court judgements, if the wife is earning well and self-sufficient, then maintenance is not mandatory. However, equitable division of marital property is still necessary in a divorce.
The figure of 1/3 salary is for a non-working wife or where the wife's income is very much less than the husband's income. In this case 1/3 of the husband's income is given as maintenance to enable the wife to maintain her earlier level of living.
Maintenance for the children is separate and has to be shared by the husband and wife according to their income. If wife is not earning, then the entire maintenance for children is also borne by the husband.