The .com zone file is updated every few minutes. Caching behaviours will vary significantly. Frequently a significant fraction of traffic can be using new nameservers within minutes, with a long tail of traffic with older information.
Each TLD does their own thing. For example, last time I checked, .ca only seemed to be serving a new zone file every few hours. How long new nameservers take will depend on your luck in terms of where you are in their refresh cycle.