Pension, profit sharing, stock bonus, annuity, or other employee trusts established by employers for the purpose of distributing the income and principal of such trust to some or all of their employees, or the beneficiaries of such employees, shall not be invalid as violating any laws or rules against perpetuities or restraints on the power of alienation of title to property; but such trusts may continue for such period of time as may be required by their provisions to accomplish the purposes for which they are established.