I would argue that some of our top referees are getting too many - top referees in Germany, France, Spain and Italy are getting no more than 20 games in a season (fewer in most countries) - Oliver and Taylor got 28 matches each this season. They could easily spread the appointments out better so the less experienced referees get a few more games.
France (38 rounds):
The most matches anyone got was 20 (Brisard, Lesage and Buquet) - Turpin got 19
Spain (38 rounds):
The most matches anyone got was 21 (Gonzalez Fuertes and del Cerro Grande) - Lahoz got 18
Germany (34 rounds):
The most matches anyone got was 17 (Grafe and Brych).
Italy (38 rounds):
The most matches anyone got was 18 (Mariani) - Orsato got 15