I never tested but in the help I found that you should do as follows :
1. Click File > Open Suite and then select a suite.
2. Click Suite > Edit Runtime.
6. Set the Time information. You can select one or more of the following:
Duration of run: Specify the maximum number of seconds for the suite to run. A value of 0 imposes no time limit on the suite run.
Initialization time: The maximum number of seconds for all virtual testers to confirm that they completed initializing. If you have changed the number of start test scripts, make sure that you set this time high enough.
Suppress timing delays: Runs a suite very quickly because all timing delays in test scripts are suppressed. Select this option if you are testing a suite to see whether it runs correctly and you are not interested in the timing delays. Note, however, that this creates a maximum workload on the server, Local, and Agent computers. Do not suppress timing delays if you are running a large number of virtual testers.
Initialize timestamps for each test script: Indicates whether timestamps are carried over from test script to test script or are reinitialized with each test script.
So the only way to play a suite or a scenario during a certain amount of time is to play with the number of iterations ?
I tried like said Corinne : to specify the maximum number of seconds for the suite to run. (A value of 0 imposes no time limit on the suite run.), but this only imposes a maximum time that the suite cannot exceed. If I choose 360 sec and the suite finished the first iteration after 50 sec, the suite finishes.
Since my suite contains a ceratin number of scnario, do I have to calculate the needed number of iterations for each scnario to play for a given perid ?