I'd like to use an Ea15K for another oil change to reach the 15,000 mile mark with a single filter. Is this considered safe?
If your engine is clean inside - - I don't see why not. That is likely a very robustly made filter. (Donaldson?)
Back in the mid-1990's, I ran a Motorcraft FL-1A on a 400M 2bbl V8 in a Ford F250 for 30,000 miles (3x OCI's), and when I cut it apart it looked perfectly fine.
No "failures" of any kind, and just some carbon(?) chunks between the pleats that were just big enough to make it through the oil pump screen.