mindless and nonsense herd instinct for most NNNNN names with few exceptions (imo), just like most LLLL domains. Many number combinations are basically useless. So are many letter combinations.
I would rather invest in pronounceable brandable LLLLL.coms which can be used by real endusers (start-ups, etc.) instead of these.
As a side note: meanwhile even low quality LLLL.coms a la QWZY drop and are sometimes available at closeouts or dropcatch for very low xx.
These are all the so called "incest market" amoung domainers which is in my opinion without prospects and will totally collapse sooner or later.
Higher quality CVCV, VCVC, etc. names of course will keep their value and maybe even increase in value. Also some nice NNNNN names belong to this group. But most don't. Quality is the key.
Just my opinion based on my own observations and experience of course.
Others might disagree.
As for NNNNN domains: i can find available ones daily. Usually they are available for few hours up to 1 day after drop before someone takes them.