Just to kick this question up.
I've had one observation I feel I could attribute to the staleness of linking pages... where some months back I noted that a client was slipping, and noted that too many of the inbound links to the home page were coming from old, stale pages, some of which were grey-barred.
Re freshness... I've observed that inbound links can take some months to show full effect. It's hard, though, to separate age factors from other upstream effects that are acting on linking pages.