Keep having to run Add-AzureAccount every day in Powershell

Hi,

Each day that I use Azure Powershell and run my first command I keep receiving the following message

"Your Azure credentials have not been set up or have expired, please run Add-AzureAccount to set up your Azure credentials"

I run Add-AzureAccount without any problems but its a bit of a pain having to do this every day - any ideas why it keeps forgetting about my account / any way of preventing this happening?

Thanks in advance