You're only considering fairness for you and your group, not the fanbase.
Me and my Dad both have 23 years. Say the lad next to me had one year, our average would be 15, rounded down to a full year.
That means a lad whose paid £700 for one year of tickets gets a choice ahead of thousands of others who have likely paid more than 12x that amount over the years (accounting for price increases). That may seem fair to the 3 people who are kept together, but its absolutely not to the thousands of others. If you look at that scenario happening on multiple occasions, the number of those who benefit increases, but the negative affect on others goes up much faster and rises exponentially.
if everyone who goes has one theyl get one?
then the extra to the waiting list?