I can't speak for the other rental companies, but with National you'll earn Executive Elite status once you hit 85 rental days. As an EE, you get 1 free day for every 5 credits and there are almost no restrictions. You can do one-ways, rent a Chevy Tahoe or Cadillac XTS. After you get EE status, you'll keep it for an extra 14 months after the year ends and you'll typically have a choice of either Mid-size SUV or Premium car upgrade with a mid-size booking which is important if you have a family and will be using your status for personal vacations. I know the other companies aren't as generous with upgrades as National.