I have built base and connected this to 4 different “towers” through horisontal elevators. Does this decay timer work on each ones by visiting my base, or should i go through them all each time?
you need to go in proximity of those if they are not linked by building piece (so considered as one part by engine game),
so not totally sure, but i think elevator do not count as building piece but as a placeable, and placeable dont give continuity in building system, so normally game engine consider you have 4 differents base.
now the area to refresh a decay timer is wide, you don’t need to be on the building, if you are walking near at a certain distance it works too (but i don’t know the exact distance, just that this is wide)
and to conclude you should consider TOS of funcom that do not like large land claim on online official server, as their admin can see it as an infraction and erase your building and give you a temporary ban if they consider you don’t respect their rules (sadly rules after one year are still not clear)
so i would recommend you to not build large, but more in high, as they have less problem with that
Ahh i see. Also, i have built these towers to take only 1 foundation spot from the ground. These are for faster travelling. I wonder why to allow us build these, if we cant use them 
@azaroth
i agree, if limitation it should be in game, and not arbitrary 