Guilds can currently build an obelisk and then by tearing it down for salvage, and giving the materials to another guild member who then builds a slightly bigger obelisk gain a materials advantage over others, by not having to use as many materials for each successive obelisk.
Therefore, an obelisk shall have to remain standing for a minimum period of 31 Real time days.
This cannot apply only to obelisks participating in test, as terms of the test may not be altered by governmental decree.
(See also: Laws)