J&M those are great points!
Doing the entire floor including front is best and realistically it doesn't add a lot to the cost so there's no real good reason to just spot treat the floor. Then again this can be subjective and a matter of personal preference.
Unopened cans of POR paint/finish are good for at least two years after purchase, according to POR anyway.
I used the silver because it has such a high-solid content. I'm sure the other colors have higher-than-expected solids but POR informed me silver had the most. This is important as that allows building a thicker film which in turn is slightly more durable if the treated surfaces will be subject to wear or foot traffic. Even if not the thicker layer is a benefit.
Another thing not yet discussed is DO NOT EVER shake POR-15 finishes---NEVER! They will build pressure inside the can even with minimum air spaces inside and when opened expel product with amazing speed and volume.
A friend---honestly not me---did this so I learned from his mistake. The mess alone was frightening to even consider. Good thing I knew in advance because I almost took two quart cans to the local paint store for mixing in one of their paint shakers. Can NOT imagine the resulting mayhem.
Personal safety is a big consideration---I did my floor outside with all van doors open. Beginning at first light was done painting by noon and it wasn't until sun down I closed it up for the night. Next day doors open again---there never was any residual odor etc.
That which falls on the ground or gets on your skin is there for a long, long time--keep that in mind as it says in POR's instructions.
Anyway POR-15 is good stuff for this job. Hope to see Smurf's progress over time.