The 30-day check-in is about activation: did the customer get started, did they complete the key setup steps, are they hitting any early blockers? This is the highest-value check-in because problems caught at 30 days are far easier to fix than problems discovered at renewal time.
The 90-day check-in shifts to outcomes: has the customer started seeing results from the product, what has surprised them (positively or negatively), and are there additional use cases they haven't explored? By 90 days, a customer who is actively engaged will have stories to tell. A customer who is quiet at 90 days is often an early churn indicator worth investigating before the renewal conversation starts.
The 60-day check-in sits between the two: activation issues should be resolved by this point, but outcomes are still emerging. This is the right moment to ask whether the customer has moved beyond the initial use case, whether they've shared the product with additional team members, and whether anything has slowed them down. A customer who was fully activated at 30 days but hasn't expanded at 60 is worth a conversation before the habit solidifies around only the features they already know.