Announce partnerships that are live and verifiable, not partnerships that are "planned" or "in development." The market has learned to discount vaporware partnerships — a signed MOU with no integration does not move the needle. The ideal timing is to announce after the integration is functional and before TGE, so that users can verify the partnership is real and factor it into their assessment of your protocol.
Stacking announcements in the 2-4 weeks before TGE can generate momentum, but only if each announcement represents something tangible.