Cached RRs for very short duration?

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Hello.

It seems that few requests from my BIND  (v9.2.1) installation are being 
satisfied from the cache.  At least that's what these stats suggest to 
me:

+++ Statistics Dump +++ (1075968122)
success 9304
referral 0
nxrrset 160
nxdomain 221
recursion 9571
failure 62
--- Statistics Dump --- (1075968122)

I actually am getting some caching.  If I do a look-up with dig I get the 
expected response.  An immediate second look-up of the same domain returns 
the data much quicker.  Obviously that data was cached.  

It seems to me that caching is being done but that the data is expiring 
very quickly.

Any comments on this?

Thanks.

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