Fencer: Found it already on the paid membership details for rooks....

1.2.2) Brain Rook

A player with Brain Rook membership level can use up to 35 vacation days a year. After some vacation days are used, it is possible (twice a year) to get some extra days (during the same year) if the membership is renewed by another year (or longer period) - 10 after the first renewal and 5 after the second one.