as far as I can see looking quickly, as long as its within a week theyd get the xp… the xp records are dropped (Assuming more records are inserted) after a week it seems.
this system of returning to the beacon to get your xp is because we cant award xp to a user is offline/on another world so they get queued up instead hoping the character will return to claim them.
there is technically a beacon-wide limit to how many records can be stored before old ones just start getting dropped too, seperate to the 1-week cutoff; but that limit is currently set STUPIDLY high (stupid like the server will probably run out of ram before they get hit…)