Aaron, I use a Sawyer viral filter, which has very similar specs compared to First Needs, in a gravity configuration. I haven't timed it but I know it doesn't take anywhere near 13.5 minutes per liter.
However, the trick with this one at least, is to prime the filter before your trip by backflushing is with the faucet attachment and leave the water in it!
This system doesn't save weight; the gravity bag + hose + dry filter weighs 9.6oz but with the wet filter, it all adds up to 14.9 oz.
However, it does save work and it filters everything, including viruses from swamp water, without any waiting or chemical side effects.
I use a Steripen Adventurer in clear mountain streams and with either system, I carry chlorine dioxide tablets as back-up.