Drop sales timelines and just stay top of mind. Tell people plainly you're there to build a relationship for the long term.
Standard sales practice says that if someone isn't buying now, you mark them closed-lost and maybe put them on a nurture campaign for six months. If you're building a relationship, abandon the timeline. Your job is to hold enough mindshare that when an opportunity comes up on their end, they think of you. Saying that out loud helps. People are bombarded with "buy now," so someone who clearly isn't expecting a purchase stands out. Raising our first venture round, I got similar advice: meet investors when you aren't raising.
I spent my early career as a developer, yet my team used to call me one of our best SDRs. All I really did was wander convention floors and hotel lobbies catching up with people, year after year. Those relationships often turned into "actually, we've been meaning to reach out." I'd introduce them to our sales team, since I was the worst at deal construction, and keep in touch as if nothing else was going on.
(adapted) "I'm just hoping to build a relationship with you, so we can work together someday, whether that's six months or six years from now. I'm in this for the long term."