Be sure to check the terms and conditions for the fare. You may find a cheap Q or V fare basis listed, but the Ts&Cs might state that it is only available monday to thursday, requires saturday night stay, and valid only for departures between say Nov 1st and Dec 15th.

Looking for a flight is peek summer season or over christmas may show V or Q available, but if the Ts&Cs for a given fare are not met, then it won't be offered. The best available fare for your given trip should be offered (which may be a more expensive V or Q fare, or a completely different fare class).

DAK