  Let $\mathbb{E}_d$ denote the little discs operad for $1 \le d \le \infty$
and let $\mathcal{C}$ be an $\infty$-category all of whose mapping spaces are
$n$-truncated. We prove that when considering $\mathbb{E}_d$-monoids in
$\mathcal{C}$, all coherence diagrams of arity $>n+3$ are redundant. More
generally, for an $\infty$-operad $\mathcal{O}$ we bound the arity of the
relevant coherence diagrams in terms of the connectivity of certain operadic
partition complexes associated to $\mathcal{O}$.
