6 monster lairs in a 50 square mile area (5 x 10 miles) seems high but not outlandish
especially if they're man-sized or smaller; it mostly depends on what they eat and what the food
supply is like. A big dragon might have a 900 square mile (30x30) or more hunting range,
but most creatures will have much smaller ranges. Hunter-gatherer humans & similar man-sized humanoids likely have a density between about 1/sq mile (though much lower in extreme desert) to 10/sq mile (very fertile areas like the Pacific Northwest of N America). Mixed herder/hunter types
will have a higher density; Small creatures like Goblins can be much higher, for 3' tall
creartures 8 times as many, while Large creatures like Ogres will be much lower - a creature weighing 5 humans will likely need 5 times the hunting range. Farmer density goes from about 10/sq mile in barren areas like the Scottish Highlands to 100/sq mile and above, medieval France 118/sq mile, can be much higher with intensive rice-paddy agriculture.
I used 1 mile/hex maps in my Yggsburgh game, based off Gygax's 1 mile/hex map in
that book, which covered a 50x50 mile area. That works really well for getting to know
an area in depth, which makes sense for settlement/colonisation. Gygax has a campaign's worth of monster lairs and dungeons in that area.
Doing a new map every 2-3 adventuring days seems excessive, at the very most I'd do 1 map
per Tier. Eg you could do a 1 mile/hex map for levels 1-4, 3 miles/hex for levels 5-10,
10 miles/hex for levels 11-16, and 30 miles/hex continental map for levels 17-20.
Read more: http://www.enworld.org/forum/showthread.php?478910-Hexcrawls-wilderness-adventures/page6#ixzz42ImcocBT