Got the two more pens a couple days ago, and finally got around to testing them out today.
For lack of AAA's I used a single 10440 with a spacer instead the regular AAA's so obviously the voltage is somewhat higher... ~3.7 vs ~3.0.
Tested all three pens, including the original I got last time.
Original pen hit hit ~30mW very quickly than plateaued for about 15 seconds... after which it went up to a pretty impressive peak of 59mW, and stabilized at around 50mW, starting to drop off after 1:20. This pen has a weird tendency to pulse at times, but it does work just fine.
Onto the new pens...
One was lackluster although perfectly in spec. Hit 31mW, evened out at ~28mW and stayed there. Very stable.
The second one blew me away. Hit a peak of 71mW I tested it three times just to make sure... and all peaks were around 70mW. It doesn't stay there for too long, but the downward curve is slow and very even.