Yes, the SORACOM platform has a mechanism that will disconnect your Air SIM session when the session is idle for approximately an hour.
In addition, a roaming partner carrier may disconnect your session earlier if there is no communication from your device to its cellular radio facility. However, the details of each partner carrier's timeout periods are not available, so you will have to perform some tests to determine the relevant timeout period.
To Keep the Connection Alive
If you require your session to stay alive for a long period, ensure you use an appropriate technique such as periodically sending keep-alive messages from your device to your server.
A session may also be disconnected due to varying network signal strengths or other environmental reasons. In addition to a keep-alive mechanism, you may also consider implementing a separate mechanism for automatically reconnecting your device when a session is disconnected.