RQM tracks test execution ownership and configuration through a concept called a "Test Execution Record" (TER for short). RQM 3.0.1 adds "Test Suite Execution Record".
You may have a Test Case and Script to "Validate Web Application Login". You may then need to test that against both Internet Explorer and Firefox. In this scenario, you'd have 2 Test Execution Records for "Validate Web Application Login" - one with a Test Environment of "Internet Explorer" and another with a Test Environment of "Firefox". You can then assign those TERs to individual testers to run. TERs are also linked to Test Milestones or Iterations that are defined in your Test Plan so the TERs are really the central planning asset when it comes to ownership, when to run a test, and how to run it.
More background: http://publib.boulder.ibm.com/infocenter/clmhelp/v3r0m1/topic/com.ibm.rational.test.qm.doc/topics/t_add_ter.html

Realized I missed the second part of your question "how long?".
Test Cases can have a weight associated with them. This is a numerical value used to represent the complexity of the test. It is up to your organization to define and agree to a convention - i.e. 1 pt = 1 hour, etc. TERs inherit the weight of their Test Case, and you can override the value (for instance, running on Internet Explorer takes 1.5 times as long as Firefox).
Reference: http://publib.boulder.ibm.com/infocenter/clmhelp/v3r0m1/topic/com.ibm.rational.test.qm.doc/topics/t_add_weight.html

Hi Matt,
What kind of information you are looking for as centralized.
I may help you if you explain your question little more.