1. A system, comprising: one or more computing nodes, each of which comprises at least one processor and a memory, wherein the one or more computing nodes are configured to perform: estimating a value for each of one or more spatial dimensions of an item in a materials handling facility dependent on corresponding spatial dimensions of each one of two or more separate dimensionally-constrained environments in which the item has been handled in temporal succession, wherein: each of the two or more separate dimensionally-constrained environments comprises a container or other apparatus in or upon which the item was received, stored, packed, shipped or conveyed, or a portal or path through or upon which the item was conveyed; and the item was handled in each of the two or more dimensionally-constrained environments in temporal succession, either individually or together with one or more other items; and performing a subsequent operation in the facility involving an instance of the item that does not require knowledge of an exact dimension of the item, wherein said performing comprises using the estimated value of at least one of the one or more spatial dimensions of the item as its practical dimensions.