the successor trustees shall be exonerated from any liability in connection with the making of such discretionary payments. the trustee shall not be under any duty to see to the application of the payments so made and the receipt by such person shall be full acquittance to the trustee. if at any time the trustee, in his sole discretion, shall determine that the continuance of any trust created under this instrument is unwarranted in view of its size, the trustee may terminate such trust and distribute the balance thereof to the beneficiary or beneficiaries for whom the trust is named. notwithstanding any provision contained herein to the contrary, the trustee (including any successor trustee or trustees) shall have the power to merge any trust created under this instrument with any other trust or trusts created by me if the terms of any such trust or trusts are substantially similar and held for the primary benefit of the same persons.