1) the 2 year minimum threshhold comes from Rev Rul 71-295 http://www.charitableplanning.com/document/666344 (ran across it last week answering another question) Not sure where the 5 years of participation service originates but I know of a plan that has a similar 2 years seasoned / 5 years participation service combination.
2) Rev Rul 1980-276 says in part: "The attainment of a stated age in a profit-sharing plan is merely one of several events that may be designated as fixing the time for making distributions from the plan. In view of the definition of normal retirement age found in section 411(a)(8) of the Code, and in the absence of any statutory prohibition or limitation, a profit-sharing plan may specify any age for distribution of benefits and, also, any age for normal retirement if it is less than the later of age 65 or the completion of 10 years of participation."
So you could have any age.
Note that 1.401(b)(1)(ii) uses the word "or". So in my opinion, you could eliminate the attained age requirement entirely. The plan I mentioned above did not have an age requirement, just the 2 years seasoned /5 years participation service part of it. But [disclaimer] consult an ERISA atty who can review the actual language of your plan.
Edit:
found it! the 5 year participation rule comes from Rev Rul 1968-24 http://www.charitableplanning.com/document/676509