The agent’s answer
Roughly the last five years is Donovan's recency rule, grounded in market reality rather than fashion. Older titles, even recognizable ones, may no longer command the place, success, or appeal they once had, and a book that mattered in the 90s might not translate now. He extends this into a caution against chasing trends: writers can call back to a trend, but their book should set itself apart and offer something refreshing, because the publishing pipeline introduces roughly a four-to-five year gap between a comp's pitch and a writer's eventual release, during which the market can change entirely. He also connects recency to the submission stage, where agents lean on P&L sheets and concrete sales data, which is easier to assess for recent comps with a known, dedicated readership.