[44net] Performance of DNS

I often experience relatively slow lookups of DNS records in .ampr.org and 44.in-addr.arpa. Not every time, but lookup times of 2-3 seconds occur quite often, especially for the first one in a series (the TTL in the zones is only an hour, so there is little caching). 44.in-addr.arpa also sometimes fail for existing hosts, to succeed when they are re-tried later. Do other people see this? It looks like there are 7 DNS servers, which seems to be plenty. Are they overloaded? Do we need or like to have more DNS servers? Should I volunteer to provide one? Or could there be another reason for this phenomenon? Rob