The astral link is created between an actual tangible astral form (an activated focus, a medicine lodge, an active spell, a spirit, the astral form of a magician using astral projection etc) and whoever is responsible for it. An astral observer who assense the astral signature of these actual tangible astral forms can track their links through the astral plane back to their sources.
Whenever the astral form vanish from the astral plane (for example if the spell expires or is no longer sustained) the astral link is no longer active but it will still have an intangible astral aura that will still carry the owners astral signature that is fading away. As long as it have not faded away it can still be used to track whoever was responsible.
A focus that is deactivated will also get an intangible astral aura that will carry its owners astral signature, but unlike a preparation or spell that is no longer sustained the aura and the astral signature of a focus will not fade over time. There is no time limit where you can no longer use Astral Tracking on the focus. However, for each passing hour since the focus was active the threshold for Astral Tracking increase by 1.
This 1 hour.. is that an hour spent in place studying the spirit, focus, etc or is that an hour spent actually tracking the link by continually moving astrally from the object's location toward the person its linked to in a more literal sense of "tracking"?
You need to take a successful astral perception test to sense the astral signature (this is where the "studying the spirit, focus etc" comes in).
If successfully sensing the astral signature you may take an extended test on Astral Tracking (this is where the "1 hour" comes in, it is the interval time for each die roll in the extended test).
If the Astral Tracking test is successful then whoever was responsible is located.
...or are you 5 minutes short of knowing exactly where to go but made no partial progress of any kind?
Rule wise an extended test will be successful once you reach the threshold. Unless explicitly mentioned 'partial progress' will not be 'saved' in case you fail the test (you would have to start all over from scratch).
What if im trying to track through a focus that was bound a year ago.
It will still carry the astral signature of its owner, but the threshold for Astral Tracking will increase for each hour since it was active (since it was deactivated).
Being bonded is different from being active.
A bound focus that is activated have an astral signature and an active astral link (there is no increase of the threshold for astral tracking while the focus is active).
A bound focus that is deactivated also have an astral signature but it no longer have an active link (there might be an increased threshold for astral tracking while the focus is not active).
people should avoid ever turning off their foci if possible
You got it backwards. It is not an increased threshold since the astral link was originally activated, it is an increased threshold since the astral link was [last] active.
So now we're back to someone being tracked through the bond of a focus rather than its active state.
The threshold for Astral Tracking will increase for each hour since it was deactivated.
All of the tracking rules refer to an astral "link" which, for a focus, must be that bond.
The astral link is active when the focus is activated. For each hour since the focus was deactivated the astral tracking threshold will increase by one.
how does tracking someone through their lost, inactive, but bonded focus work?
First of all you need to take an Astral Perception test to successfully sense the astral signature.
Once this is done you do an Astral Tracking extended test Threshold for Astral Tracking is increasing for each hour passed since the focus was deactivated.