Thomas,
Can/may bindings directly access the persistence store? The binding has no knowledge of which Item is bound to it (apart from what it gets from the BindingProvider), let alone what type of persistence is used, the strategies and so forth. So far I think not a single binding had the need to access historical data, e.g. it was all part of userland/runtime.  But like Paul mentions, additional calculus features in the persistence classes would be helpful. Apart from maxSince etc, there should be a totalSince or alike, taking into account things like the time elapsed between two entries in the persistence store.