TTN now seems to store every single gateway status message in mongodb, I hope with some limit or expiration because else it would truly cost millions to eventually billions of (useless?) records.
Wouldn't it be better to save just the most recent one? (so just one key/value per gateway that is updated every new status packet) 
also the question is if mongodb is the most economical solution for such simple K/V storage.
secondly I think TTN should be able to adjust the status packet frequency from their servers, it could for example respond to the status message of each gateway with a new interval number in seconds. like that the frequency is adjustable dynamically from the network.