Workload Collector Retention Time

Does anybody know, how i can change the retention time parameter of the statistic data stored in stat.dat for sap-release 7.0 (2004s)?

In release 6.2 there was -> Collector & Perf. Database -> Workload Collector -> Control

and stat/max_files could be changed in transaction RZ10,

like

http://help.sap.com/saphelp_nw04/helpdata/en/ff/0ae73ac6e7ec28e10000000a114084/content.htm

In release 7.0 i can change the stat/max_files, too, but i don't found any possibility to change the retention time.

Transaction ST03G shows the time but i can't changing anything.