I haven't actually played them yet, but I have a save file dedicated for them all. I do intend to play them eventually but I'm enjoying my current save. I usually make the sim for each Scenario and place them in my save so I can play them when I get around to it.
As for them being limited time, I'm not a fan of anything with a time limit. That being said, I understand if they were all still available that would (or could) become a performance problem in the future. Of course, I'm not too tech savvy so I really don't know if that's even a issue, just an assumption.