Adobe Sign API in C# - Expiring Access Token

Hi,

I'm working on integrating Adobe Sign in to one of our client systems. They've provided me with an access token which works for awhile and then seems to expire.

Is there a way to prevent the key expiring or something my client can do to stop it expiring?

I've been successful in retrieving a transient document ID in an ashx but the development is progressing very slowly due to the key expiring. I was using a trial key which expired every 10 minutes but now I'm no longer able to use this. My client has a full account as far as I'm aware so I assume they can provide a key which cannot expire?

Maybe I'm missing something.

Any help greatly appreciated,

Thanks,

Sonny