Synchronisation issue with SharePoint FBA claims-based

In a SharePoint 2010 extranet I apply a custom membership provider for Forms-Based Authentication. The provider works like a charm, external users are authenticated when logging on with valid credentials, and denied access otherwise.

However, after functioning smoothly for a while, we suddenly encountered the error below when trying to logon via FBA:

[FaultException`1: The context has expired and can no longer be used. (Exception from HRESULT: 0x80090317)]
Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.ReadResponse(Message response) +1161205
Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst, RequestSecurityTokenResponse& rstr) +73
Microsoft.IdentityModel.Protocols.WSTrust.WSTrustChannel.Issue(RequestSecurityToken rst) +36
Microsoft.SharePoint.SPSecurityContext.SecurityTokenForContext(Uri context, Boolean bearerToken, SecurityToken onBehalfOf, SecurityToken actAs, SecurityToken delegateTo) +26060225
Microsoft.SharePoint.SPSecurityContext.SecurityTokenForFormsAuthentication(Uri context, String membershipProviderName, String roleProviderName, String username, String password) +26063596
Microsoft.SharePoint.IdentityModel.Pages.FormsSignInPage.GetSecurityToken(Login formsSignInControl) +188
Microsoft.SharePoint.IdentityModel.Pages.FormsSignInPage.AuthenticateEventHandler(Object sender, AuthenticateEventArgs formAuthenticateEvent) +123
System.Web.UI.WebControls.Login.AttemptLogin() +152

Logon via Windows authentication had no problem, only the FBA route. Since there had been no software or configuration changes for the custom provider, the cause must be found to be at [SharePoint Farm] infra level. In the Application Eventlog I noticed the following Error log: An exception occurred when trying to issue security token: The context has expired and can no longer be used. (Exception from HRESULT: 0x80090317).

This steered me within the direction of the generic Security Token handling in the farm, instead of the context of the extranet webapplication self. As first attempt I decided to restart the SecureToken Service Application. And voila, this was already sufficient: problem resolved. That is, for a while... The problem namely structural reappears after a couple of days of minor or no activity in the SharePoint farm. It looks to me as something of a clock timer synchronization issue within the SharePoint farm, that can for a period be prevented by timely 'refreshing' the SecureToken application pool.