How do you know when to do maps?

From what I know, you can do maps in order to get books that let you prestige your equipment.

However as I found out there's a limit to this, after a while the final reward changes from a book to something else.

I discovered that after completing a few zones that when I created a new map and ran through that, the final reward was again a prestige.

So how can I know when the final reward will be a prestige item? How much of the world do I need to do before getting more?

Each world will generate maps of a level equivalent to the world number - maps created while on world 9, will be lvl 9.

There are currently only a set number of item unlocks per level. So once you've collected all the level 9 items, there will be no more until you create a map on world 10 (a level 10 map). However, it may be worthwhile to sit on a map and grind out resources for a bit so that you are better prepared (better gear / more gyms / more trainers) for the next level.

Last I've checked, starting at lvl 6 (I lost track where in here the Mansion unlocks):

• Map lvl 6
  • Shield, Dagger, Boots (mk II)
• Map lvl 7
  • Mace, Helmet (mk II)
• Map lvl 8
  • Polearm, Pants (mk II)
• Map lvl 9
  • Battleaxe, Shoulderguards (mk II)
• Map lvl 10
  • Greatsword, Breastplate (mk II)

Map lvl 11 starts to unlock the mk III gear (Shield, Dagger, Boots), so presumably it cycles every 5 levels.

If you skip a level, for example if you complete world 8 without exploring any level 8 maps, the next world's maps will contain the otherwise 'missed' items. So the lvl 9 map would contain 4 items (Polearm, Pants, Battleaxe, Shoulderguards) rather than the usual 2.