How long does it usually take nameserver changed to work for all my website members?

If I change my website's nameservers from say:



ns1.123.com

ns2.123.com



to



ns1.abc.com

ns2.abc.com



How long would the changes take before I can be reasonably assured all my website viewers are seeing the ns2 version? Also what if I change the IP address asigned to each ns. thank youHow long does it usually take nameserver changed to work for all my website members?
It can take up to a week or two for various DNS servers to resolve the change, especially if you have a low traffic site. You could give your members your new address as an IP (http://123.456.789.000) to avoid the DNS update delay.



Don