[rules-users] Why does Drools' RuleBase.addPackage() Behave This Way?

I am benchmarking Drools 4.0 and received excellent results in rule execution. With our non-optimized test rule set and data, Drools out performed ILOG/JRules by quite a bit. Congratulations to Drools' team for a job well done. I encountered a strange behavior when trying to test the performance of rule registration, meaning to add Package's to a new instance of RuleBase. I ran the same test 5 times in a sequence, and the RuleBase instance was discarded right away. The test ran with different different number of packages, 20, 50, 100, and 200. The results are as the followings: Added 20 packages to rulebase in 0:00:0.15 Added 20 packages to rulebase in 0:00:0.21 Added 20 packages to rulebase in 0:00:0.21 Added 20 packages to rulebase in 0:00:0.301 Added 20 packages to rulebase in 0:00:0.18 Added 20 packages to rulebase 5 times in 0:00:1.051 Added 50 packages to rulebase in 0:00:0.17 Added 50 packages to rulebase in 0:00:1.422 Added 50 packages to rulebase in 0:00:1.252 Added 50 packages to rulebase in 0:00:1.322 Added 50 packages to rulebase in 0:00:1.331 Added 50 packages to rulebase 5 times in 0:00:5.497 Added 100 packages to rulebase in 0:00:0.19 Added 100 packages to rulebase in 0:00:5.278 Added 100 packages to rulebase in 0:00:5.297 Added 100 packages to rulebase in 0:00:5.228 Added 100 packages to rulebase in 0:00:5.327 Added 100 packages to rulebase 5 times in 0:00:21.32 Added 200 packages to rulebase in 0:00:0.22 Added 200 packages to rulebase in 0:00:21.691 Added 200 packages to rulebase in 0:00:21.481 Added 200 packages to rulebase in 0:00:21.642 Added 200 packages to rulebase in 0:00:21.341 Added 200 packages to rulebase 5 times in 0:01:26.385 As you can see, the timing of creating first RuleBase instance is always good, while the subsequent one's were very bad. Is there an attribute I could adjust in configuration to improve the performance for this scenario? Please advise if there is other alternatives. I would be glad to provide details if needed. Your help is greatly appreciated! -Ming