I think we are confusing between miles earned and the perks needed each year to retain certain a level or benefits. United for one, the miles earned/accrued no longer expire, however, in order to maintain a tier level each year, one needs to earn certain # of miles.
From a Royal perspective, Casino Royale one needs X number of points each year to retain a certain level, eg. Prime = 2,500 points. At the beginning of year, it begins at 0. The tier levels are distinct from the C&A levels and accrue add'l benefits. eg. unlimited drinks in casino, discount on internet package, free cruise(s), etc.
Casino Royale year starts April 1 and ends March 31 of following year.