Frankly, the story of Ashaman tiring because they had to keep the gateway open is a mistake by Sanderson.

In CoS, Sammael opens gateways for the Shaido and Graendal notes that he had tied some of the gateways off with a loose knot to dissipate after a predetermined period of time.

And in KoD, Rand and Logain make Deathgates that open and close to random locations, tie off 6 weaves at once and start weaving more Deathgates.

So there is actually no need to actively hold open a gateway. You can just open it, tie it off and move on to creating your next gateway immediately.

And as RJ said, a tied off weave can exist for eternity if you tie a permanent knot in it. No need for elaborate cuendillar contraptions.