Low cost carriers in Europed use or used that "trick" and they had a few taxi in flame outs.
Long range flights are usually to major airports, which all meet the two runway, etc, etc... But they usually get congested without previous notice.
Once again, when it comes to fuel saving measures lime thet, captains have to be very conservative and take positive accion early when ot seems that you will burn more fuel than anticipated. In this case, advise ATC and declare mayday.
In some airlines it is policy to declare emergency even before reaching the final reserve, if it is obvious that you are going to burn a part of ot before landing