In reply to cgales:
The regression will stay during the whole duration of the project and will be run nightly. At the end of the project, if I added 3 months before 10 extra tests with random seeds for bug hunting (bug out of the functional space), I would have run 1000 occurrences that what I meant by spreading over time....
The goal of functional coverage + randomization with the use of test ranking is to make sure that I can reach closure in a deterministic way. Bug hunting is not deterministic, I can always do more.
I agree with what you suggest, i.e. try to eliminate the bugs as soon as possible hence I think that bug hunting process with random seeds should be carried out mainly by the verification engineer who wrote the test by running locally many random seeds, and only to a small extend by the nightly regression.
10% addition on the nightly regression dedicated to test running with random seeds seems reasonable (the other 90% being ranked fixed seed for reaching 100% coverage). What is your opinion?