when do you know its time to ditch REST for gRPC?

hey everyone, ive been building out a few internal microservices and we've primarily used REST with JSON for communication. its been working fine, but im starting to wonder about gRPC. for internal services, especially where performance is a bigger concern and the client/server contracts are pretty stable, gRPC seems like it could offer some nice benefits like performance and type safety. has anyone made the switch from REST to gRPC for internal communication? what was the tipping point? were the gains worth the added complexity?