By default, the VMware vSphere Client in VMware vCenter Server and VCSA is configured so that your session expires after 2 hours.
However, in the case of a lab (test environment), it may be interesting to extend or deactivate this expiration time to avoid reconnecting too often.

Note: the file to modify is the same whether you are using the Windows version of VMware vCenter Server or the virtual appliance (VCSA).
However, the method to modify the file is not the same since the operating system is not the same.

1. Disable vCenter Server web client timeout on VCSA
2. Disable vCenter Server web client timeout on Windows Server

1. Disable vCenter Server web client timeout on VCSA

If you're using VCSA, which you probably are since the Windows version has been deprecated since version 6.7.

To begin, enable SSH access in the “VCSA” appliance settings.
If necessary, refer to our tutorial: VMware vSphere 6.7 - Enable SSH protocol on VCSA.

Then, connect by SSH to VCSA using PuTTY.

By default, you will be in the VCSA appliance shell.

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Command>

To modify the necessary file, you must therefore use the "shell" command to access the Linux Shell.

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shell

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Shell access is granted to root

Go to the “/etc/vmware/vsphere-client” folder.

Bash

cd /etc/vmware/vsphere-client

Edit the "webclient.properties" file found there using the "vi" text editor which is already pre-installed.

Bash

vi webclient.properties

This is displayed.

Find the "session.timeout" property in this file using the "/" command in "vi", then press Enter.
Which give :

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/session.timeout

As you can see, by default, the web client session expires after 120 minutes (= 2 hours).

Press "i" to enter "Insert" mode and specify "0" as the value to disable the session timeout for the web client.

Press "Esc", type the command ":wq" to save the changes and press Enter.

Now that the web client configuration file has been modified, restart the "vsphere-client" service for the change to take effect.

Batch

service-control --restart vsphere-client

Wait a little (around 30 seconds), then this will appear:

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Successfully restarted service vsphere-client

2. Disable vCenter Server web client timeout on Windows Server

If you are using the Windows (Server) version of VMware vCenter Server, simply edit the "C:\ProgramData\VMware\vCenterServer\cfg\vsphere-client\webclient.properties" file with notepad.

In this file, look for the “session.timeout” property.
As you can see in the comment just above this property, by default the session for the web client expires after 120 minutes (2 hours).
To disable this timeout, specify 0 as the value and save the file.

Then, for this change to take effect, you will need to restart the "vsphere-client" service.
However, this service is not visible from the usual Windows console (Server).

To restart this "vsphere-client" service, you will need to open a command prompt (cmd.exe) and move to the folder: C:\Program Files\VMware\vCenter Server\bin.

Batch

cd C:\Program Files\VMware\vCenter Server\bin

Then use the command below to restart the service mentioned above.

Batch

service-control --restart vsphere-client

Wait 30 seconds and this will appear in Command Prompt.

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Successfully restarted service vsphere-client

Source : Configure the vSphere Web Client Timeout Value - VMware Docs.