I largely agree with what has been said so far. I guess it depends on what is available to you cheaply what commercial maps are available off the shelf and how often you walk a particular area. For example for Bodmin moor OS publish two neat small laminated maps at 25k that cover the entire moor. I walk there frequently, so they are tucked away in my rucksack along with my emergency bivi. Just in case I get caught out with very poor visibility, as can happen quickly as the sun drops, even on a beautiful evening out on the moor.
For Dartmoor, much larger area than Bodmin moor. I have, over past years, printed out then laminated maps on A4 at various scales, that cover the entire moor. These are far easier to both carry and use than folded paper maps. From my home made library Just pick the sheet I need for the area of the moor I plan to walk that day.
A similar if more bespoke approach works pretty much any where. So prior to a visit to New Zealand, I printed and Laminated maps of all the off piste areas I thought we might walk. Four A3 sheets did the trick and took up next to no room and weight in my pack.