In general, you can usually simplify the first one to have one lifetime for both, and in the second, you’d probably want two lifetimes, one for destination and

In general, you can usually simplify the first one to have one lifetime for both, and in the second, you’d probably want two lifetimes, one for destination and the others all shared. Defaulting to the same lifetime for everything and then introducing more of them when needed is better than starting with a unique lifetime for each reference. I think you two are ultimately talking about slightly different things, your parent is trying to point out that, even if this signature is complex, it can’t get more complex than this: one lifetime per reference means the complexity has an upper bound.