Many car insurance policies are still sold for 12 months. As during a 12 month period the needs of drivers may change, short term insurance (including car insurance for three days or less) can now be secured potentially providing a better value and more flexible solution.
Several drivers of vans will either be hiring or borrowing the vehicle. This can be where van insurance for six months is necessary, when you are borrowing a van for differing situations.
For riders that are planning a summer road trip, six months bike insurance could be convenient. This may prove economical if they will only be riding while they are away.