The number isn't the problem, coordination is
A small team can technically have ten open projects. The problem isn't the workload, it's how many of those ten projects need active coordination at the same time: client questions, approvals, payment follow-ups.
A simple way to estimate it
Count not the projects, but the active touchpoints per project in an average week, how many messages, approvals or updates it needs. Two or three people can realistically sustain 15-20 touchpoints a week without burning out.
Signs you've gone over the limit
- You're answering client messages after hours, consistently.
- Deadlines start slipping not from lack of work, but from lack of time to communicate clearly what's happening.
- You no longer know, without checking, what stage each project is at.
What actually helps
A visible timeline for the client and a portal where they can check the status themselves drastically cut the touchpoints you need, the client stops having to ask, because they can see it.
Bottom line
The real limit isn't how many projects you can open, it's how many you can actively coordinate without losing the quality of communication with each client.