They changed - and were also fuzzy. There is a useful French word - 'mouvance' - it describes the web of connections, influence and control a ruler had. So one might say that the Count of Anjou brought Tours within his mouvance - that is, the Count of Touraine could at least be relied on not to oppose him, and to take his requests seriously. In the same way, the ruler of, say, Mercia, might at different times include, say, Hwicce within his mouvance - the leaders of Hwicce could be relied at least not to be hostile and possibly much more (support in war, maybe even taxes). We can sometimes trace how far control extended by looking at who turned up for significant occasions, who signed charters, whether a king could appoint officials and so on. It was tied to personal relations and it fluctuated both in depth and space - for instance a marriage might bring an area within one's mouvance, and a death remove it, or an area go from ally to core.

Lordships and kingdoms had a core area and beyond that, a shifting zone of influence.