OK, I sussed out the hookpoints,
If you make them visible via the First Mate, then stand on the hook point it tells you the time remaining.
For example, the two crew members that give us the buffs, each had 16 hours on them so I double clicked the hook point and bought another of each one for about 200 plat each. This put two tokens in my pack. Then double click the relevant token whilst standing on the hook point and it adds a further 7 days. Each crew member can be maxxed out for time to 30 days by adding the tokens.
The Post box, bar and guild chest all came from the ddo store with Turbine Points because we had to be level 24 guild to get them but wanted to see what they were like.. The Chest is good for a whole month, with another month addable with tp, or ingame 12,000 plat once we get to the appropriate level. The Bar and mail box are good for a week. I suggest we let the bar and mail box go after that seven days until we can upgrade the time on them with ingame plats, theyre pretty cheep and certainly that's better than spending our turbine points on them. We only have three or four levels to gain to get there.
Anyhoo, that's how they work. Upkeep shouldn't be too bad on the rentables as I made over 10k last night just auctioning stuff from the last two nights hunting.