How do you move power users from your free tier to paid plans?

When we launched, we were extremely generous with our free plan to lower the barrier to entry and get initial traction.

It worked for growth, but now a significant chunk of our active daily users rely on the product heavily without ever needing to upgrades. Whenever we consider shifting certain features behind a paywall, we worry about pushing away the early adopters who helped build our community.

How do you restructure your pricing tiers to drive conversion without frustrating the free users who generate word-of-mouth momentum?