Heavensward nodes actually are up only for 55 Eorzea minutes (2:45 real time). Too often I had nodes yanked out from underneath me when I was finishing a final collectible gathering.

The upside to this is that HW unspoiled* nodes are up twice every Eorzea day, offering two opportunities to gather every 72 minutes.

* - Ephemeral and Folklore/Legendary nodes follow their own ruleset, despite some similarities.