Seems to complete whilst the timeout handler is runing:

Iteration: 29
Could not find object description containing text "Class Name: jdk.jfr.event.oldobject.TestClassLoader$TestClass"
Found descriptions:
Class Name: jdk.jfr.event.oldobject.TestObjectDescription
Size: 99900

Iteration: 30
Timeout signalled after 480 seconds
Could not find object description containing text "Class Name: jdk.jfr.event.oldobject.TestClassLoader$TestClass"
Found descriptions:
Class Name: jdk.internal.vm.VMSupport
Class Name: sun.util.resources.provider.NonBaseLocaleDataMetaInfo
Class Name: jdk.jfr.event.oldobject.TestObjectDescription
Size: 99900
Class Name: java.time.zone.ZoneRulesProvider
Class Name: sun.util.locale.provider.LocaleProviderAdapter
Class Name: sun.util.cldr.CLDRBaseLocaleDataMetaInfo$CLDRMapHolder
Size: 603
Size: 622
Size: 2
Size: 121
Size: 3
Class Name: java.io.Externalizable
Size: 5
Size: 1140
Class Name: java.util.zip.ZipFile$Source

Iteration: 31
Found descriptions:
Class Name: java.time.Instant$1
Size: 3
Class Name: jdk.jfr.event.oldobject.TestObjectDescription
Class Name: jdk.jfr.event.oldobject.TestClassLoader$TestClass0153981
Size: 99900
Class Name: java.lang.ref.FinalizerHistogram
Class Name: java.lang.StackTraceElement$HashedModules
Thread Name: Attach Listener
Iteration: 1
Found descriptions:
Size: 3
Class Name: jdk.jfr.event.oldobject.TestObjectDescription
Size: 99901
Iteration: 1
Found descriptions:
Thread Name: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...
Class Name: jdk.jfr.event.oldobject.TestObjectDescription
Size: 99901
----------System.err:(1/15)----------
STATUS:Passed.

Test is running with -XX:+UseCompactObjectHeaders'