I thought a lot about the whole concept, and the reason i don't wrote earlier is, because my opinion is split in two pieces about the complete topic. Let my try to answer on all points mentioned by others (which bother me) but first let me explain my own point of view.
My Point of View
I think it's a good idea that beacons vanish after some "inacceptable" inactivity from the owning player. My main points are:
Cities of "buildings" where no one's ever active (nice to look but useless)
the core of a city will decay (less and less players) and the outer circle is the only place for new buildings. the outer circle will expand while the inner core of a city dies - no need to go in the center because there are no active players.
if we start the game we have the chance to see the world how it was designed to be (all natural) in later game states a lot of nice places will be crowded with a lot of buildings (some nice, some not). If you are inactive for a long time it would be "unappealing" if the world is full of abandoned buildings (cadaverous buildings polluting the environment)
Motivation / Treasure Hunt
for me it would be great if it would be possible to loot lost "treasures" long time after the place was abandoned (assuming that chests will take really long times to decay). this would incentive players to roame in the world and search on lost places (treasure seekers) [remember - there are NO quests]
I'm also for the fuel idea. If i know that my friend is ill (in hospital or had an accident) i can take care of his beacons and refill them.
On the other hand i can understand that it's ridiculous if you come back after a year and you lost everything. This leads me to some questions / ambiguities.
As far as i understand the concept of this game, a lot of progression is stored in items and machinery but not like in other MMOs where you spend hundreds of ours grinding for one item but also in the combination of items, the knowledge you need to combine items and tools and so on. So my first question: "If you loose your building and your tool how much progression would you lose over all ?". If it's only the time collecting the materials it's not a big lost in my opinion because you've already collected the knowledge to rebuild (time lost < 30% would be acceptable in my opinion).
Starting from the scratch can be a great possiblity for new and fresh ideas. If you are forced to search a new location (because your old is taken) you have the chance to find better spots or new people (enhance user interactions). "Why should it always be bad to start new ?" I started on 3 worlds (before the C++) and on every new place i had new ideas for buildings. sometimes i go back to my old worlds (buildings) but i would not miss them if the decay and i'd love to see what others will do with the places.
I think it is a major requirement that we will get a sort of "permanent" storage (eg. a bank account that holds items account wide and forever) where you can store your most valuable items. @olliepurkiss "Will there be a way to store items and machinery save from decay?"
"Will machines be transportable ?" If they can't be transpoted we have an other problem -> you need to left back a lot of progression if you change the world. In this case it's like a complete lost anyway and then i would have no problems with them to decay. If mechines will be transportable i hope we'll be able to store them in a permanent store.
Even if there are a lot of open questions for me (see above) i think that beacons should expire and it should be possible for others to care for your beacon (refill them). If the really vanish at some point in time it would be a good solution to get a persistent storage for you items. it should be possible for everyone to join the game once in 3-6 months and save your items. if they are not worth a single login and 5 minutes to save them (forever) you don't really care and than there should be no problem at all for you.
Notes to Others
Some random notes to others ...
I like the idea of a decay in stages / phases. This would fit into the "treasure hunt" concept (assuming your times are placeholders - they are really short). I'd like to add that chests should "NEVER" regenerate because it's nice to find a lost treasure and it would make exploring more fun IMO.
@olliepurkiss: I'd be interested in an answer too.
they will need a lot more space. You only include the beaconed area in your calcuation but there are easy ways to incease your space artificially (see later). Furthermore you miss the space players would need to collect and gather ressources (i know the regenerate - the question is still how fast) around the beacon. 3k players are really few for a MMO and i'm sure or i hope there will be a lot more players online than 3k. B2T the problem of ghost towns and heterogeneous cities (dead core, expanding outer circle) will remain if there won't be beacon expiration.
I can accept this but as said before, i don't think that "everything" has a right to remain (aforementioned reasons).
Can you explain who is minor and who is the greater part of the players here ? I don't fully understand that part.
Good point. This would be cool.
He doesn't play therefore it is useless he blocks space in the city core would be my reason.
You can lock in not beaconed space - where world regenerates - inside a beacon (the beacon + a shell of glass (eg. glass) acts as shell for the unprotected area inside). This is also an artificial possibility to enlarge your beacon without great effort if you don't care what inside (the inner part will regenerate). This formular (where n is the endge lenght of beacon plots inside to protect) describes the beacons needed to protect a area of n beacons plots inside (cubic areas). There is also an other advantage of the "shell" concept because you save a lot of beacons and you can enlarge your building (descirpted by this formular - you can see that you save ~230% if you protect an area of 10x10x10 beacon plots [80x80x80 blocks]).
I also asked @lucadeltodecso if it will respawn random but i don't got an answer yet.