No other class I know give the same power in the same way, you cannot progress beyon 10 level in e PrC unless you are Epic and as it was said previously starting at 11 level you have an alternate progression in The Mystic Theurge class, one level for cleric, one level for wizard.
EPIC LEVEL BASICS
Epic characters—those whose character level is 21st or higher—are handled slightly differently from nonepic characters. While epic characters continue to receive most of the benefits of gaining levels, some benefits are replaced by alternative gains. A class can be advanced beyond 20th level. A ten-level prestige class can progress beyond 10th level, but only if the character level is already 20th or higher. A class with fewer than ten levels cannot progress beyond the maximum for that class, regardless of character level.
EPIC MYSTIC THEURGE
Hit Die: d4
Skill Points at Each Additional Level: 2 + Int modifier
Spells: When an odd-numbered mystic theurge level above 10th is gained she gains new spells per day (and spells known, if applicable), as if she had gained a level in an arcane spellcasting class she belonged to previously, up to the maximum spells per day and spells known by that class. Her caster level in that class also increases by +1. When an even-numbered mystic theurge level above 10th is gained she gains new spells per day (and spells known, if applicable), as if she had gained a level in a divine spellcasting class she belonged to previously, up to the maximum spells per day and spells known by that class. Her caster level in that class also increases by +1.
Bonus Feats: The epic mystic theurge gains a bonus feat (selected from the list of epic mystic theurge feats) every 6 levels after 10th.
