No trust previously or subsequently created by an employer as a part of a pension, stock bonus, disability, death benefit, profit sharing or similar plan for the exclusive benefit of some or all of the employer's employees or their beneficiaries to which contributions are made by the employer or employees, or both employer and employees, for the purpose of distributing to the employees or their beneficiaries, the earnings or principal or both earnings and principal, of the trust, shall be deemed to be invalid by reason of any existing law or rule against perpetuities or suspension of the power of alienation; but the trust may continue for such time as may be necessary to accomplish the purposes for which it may be created. The income arising from any property held in trust may be permitted to accumulate for the length permitted by the instrument creating the trust, or, if no time is so specified, for the time the trustee or trustees deem necessary to accomplish the purposes of the trust.