[Zope] Values in transient object container not persistant?

Hello all, I just started using /temp_folder/session_data for our site and found the following behaviour. The default value for "Maximum number of subobjects"=1000 is much to low, because it is reached within minutes. So I changed it to 0 (means infinite). But if I restart the server, "Maximum number of subobjects" is set back to 1000. I think the reason for this is /temp_folder which contains /temp_folder/session_data. What should I do to keep my settings? Thanks in advance Sven