Upgrading Monuments is done when the claim radius approaches the maximum for that tier. The time window for upgrades is reported to be short, so take advantage of it when you see it offered.
In the area protected by Monument, a non-guild member can not dig, loot, claim, open, or lift Items.
As of 03/20/16 however, they can still for example gather apples.
Tip: If a non-guild member rides a horse into your guild, and get off their horse (say, to barter)(**) they must get on within the 2 minute timer, or else the horse belongs to the guild. To recover the horse requires either (1) a guild member riding it out of the guild, or (2) a guild member hiding (moved into inventory) and bartering it to the non-guild member.
(**) From experience: "OR crashes / times out of the game - while riding in another guild - and can't get back within 2 minutes
|ID||Image||Name||Max Town Claim Radius (Tiles)||Additional Realm Radius (Tiles)||Total (tiles)||Minimal sacrifice item price||Authority Skill required||Maintenance cost per in-game day/night|