Do I have to maintain the 401(k) Plan once adopted?

Yes. Treasury Regulation Section 1.401-1(b)(1)(ii) provides that a profit sharing plan is established to enable employees or their beneficiaries to participate in the profits of the employer's trade or business, or in the profits of an affiliated employer who is entitled to deduct his contributions to the plan under Internal Revenue Code Section 404(a)(3)(8), pursuant to a definite formula for allocating the contributions and for distributing the funds accumulated under the plan. Treasury Regulation Section 1.401-1(b)(2) requires that the plan be a permanent, as distinguished from temporary, arrangement, and provides a general rule that if a plan is discontinued within a few years after its adoption, there is a presumption that it was not intended as a permanent program from its inception, unless business necessity required the discontinuance, termination or partial termination.