I agree with ManFromTheBrand.
We have a "hard press" mode, and a "back burner" mode.
"Hard Press":
When someone signs up, getting in touch as soon as feasibly possible is more important than anything else you could do. (First 10 minutes if at all possible, & DEFINITELY within the first 24 hours.) After that, we encourage our agents to follow up every couple weeks for the first 4-6 weeks.
"Back Burner":
Keep in regular contact via drip emails & property updates. Call those who you have talked with at least every couple months to stay on top of mind.
80% of your energy/resources should be spent on your brand-new leads, and older leads who are actually interacting with you. Your systems should handle everyone else, leaving you with 20% of your efforts to spend on them.