Thanks to ignasia7 for the strategy information on the Blue Chest Rules. And thanks to eRiZ for the list of the blue chest locations.

Blue Chest Rules

  1. 1) Blue Chests appear all over the world map in fixed spaces.
  2. 2) Blue Chests can be opened once each per real-time 24-hour period, once each day at 00:00 or 12:00am on your 3DS clock.
  3. 3) Each Blue Chest contains random items that are set when the world map loads.
  4. 4) Blue Chest items reset each time the game loads a new map, assuming that chest contains an item, or has had its 24-hour period reset. This is ONLY thing that reloads chest contents.
  5. 5) Dragon Quest VIII checks for forced time changes in the 3DS menu, so the 24-hour period cannot be reset by changing the 3DS system time zone or messing with the system clock. It will only reset the 24-hour period all over again.
  6. 6) Each blue chest is fixed to one of 5 distinct chest ranks, containing a fixed set of randomly chosen items. Each group is generally found 1 through 5 in linear fashion to the progress of the game.

So how to abuse this? One option is to use a church save, at the closest church. A few spots are very useful for this, such as some of the small churches that dot the landscape, but for many chests, using those locations, or even churches in towns can add a lot of extra time.

So the quicksave method to the rescue for either a small bit of time saving, or a huge chunk of time saved, depending on the location.


How?

Given point #4, and that chest contents reload on a map load, find the closest location to each Blue Chest on the map, Zoom to the nearest Zoom point, and walk towards the area closest to each Blue Chest that will load to a new map, such as a town, stop-over point, a house, castle, dungeon, tower, etc. Anything that exists as a separate map from the world map and causes a map change/load.

Open the menu with "X", click on "Misc.", then "Quick Save". Click "Yes" twice, then exit back to the world map, head towards the chest and open it. If the item is undesired, exit and reload the game, and load the "Suspended" save game. Then exit again, and repeat until the desired item is obtained.

This saves a lot of time, and it makes it possible to reset the chests for desired items much easier and faster than using a church.


Chest Groups

Group 1: 50/100/150 Gold, Magic Water, Eau de Monster, Holy Water, Amor Seco Essence, Seed of Wisdom

Group 2: 100/200/300 Gold, Magic Water, Eau de Monster, Mystifying Mixture, Special Medicine, Seed of Agility

Group 3: 200/400/600 Gold, Magic Water, Eau de Monster, Rockbomb Shard, Special Antidote, Seed of Strength

Group 4: 300/600/900 Gold, Magic Water, Eau de Monster, Lesser Panacea, Seed of Resilience, Seed of Life, Gold Bullion

Group 5: 400/800/1200 Gold, Magic Water, Eau de Monster, Greater Panacea, Seed of Skill, Seed of Magic


Chest Locations

Level 1

Level 2

Level 3

Level 4

Level 5

GameFAQs wouldn't let me post this in its cheat section, so I'm posting it here. Not enough data for a FAQ. and not worth it to me to make one about it. I'll include a world map later of my own make. I just need Zenith's permission to use his.

Until then, The n00b Avenger made this makeshift one using the Brady guide as a base: