They don't PICK names to keep. I guess you've watched too much X-Files. Registrars that do not release names on a scheduled basis are simply imcompetent.
I had waited more than 17 months before I got clonecity.com; and there are other cases I heard of with looonger on-hold windows.
Some names they release, some names they don't.. Its just the way it goes. Heck, im watching a name that expired over a year ago and its still active! as in there still is a website!..makes no sense.
MOST registrars drop names regularly, each according to its own schedule - usually between 30-40 days after expiry. E.g. OpenSRS/Tucows drop theirs almost always on the 41st day exactly.