[Zope] Session Timeouts

I'm forever forgetting to reset session timeouts when I restart Zope. First, is there a way to change the default without brain surgery? The 20 minute default value that's used is deep within the __init__ for Transience objects. Is there a way to reset the timeout without reinitializing and killing all active transient objects? I looked at the code and it does not seem possible. Unfortunate, in a way, since resetting the timeout value kills all existing session sub-objects.