Answer
The clearest signal that a managed service fits is when the internal team can describe what they need but not how to build and run it themselves. A shop with one or two IBM i administrators already stretched across daily operations, PTF management, and application support rarely has the bandwidth to also become expert in replication tuning, disaster recovery testing, and 24x7 failover monitoring, and trying to build that expertise in-house often takes years and several expensive mistakes along the way. A managed HA service compresses that timeline by putting people who already do this daily in charge of the parts that require constant attention.
Buyers considering this route should still ask hard questions rather than treating "managed" as a reason to stop evaluating. Find out where the replicated data physically lives and who has access to it, what the service level agreement actually guarantees for failover time versus what it merely targets, how role-swap testing is scheduled and who initiates it during a real event, and what happens contractually if the service provider itself has an outage or goes out of business. A strong managed HA provider will answer these clearly and can usually produce a reference customer who has been through a real failover, not just a testing exercise, under their management.