The phrase "becomes tedious" describes a situation in which something becomes tiresome or boring. There are many synonyms for this phrase, which can be used to add variety and depth to your writing. Some possible synonyms include "grows monotonous," "becomes dull," "gets tiresome," "turns stale," "loses its luster," "becomes banal," "becomes wearisome," "becomes humdrum," "becomes routine," and "becomes tedious." Each of these phrases captures a slightly different nuance of meaning while still conveying the basic idea of boredom or monotony. By using these synonyms effectively, you can add variety and interest to your writing while avoiding repetition.