From my understanding there is no infinity duration in Nodal. However you can go very long.
You can zoom out and draw nodes very far apart.
In the inspector window in the documents window you can set the number of beat per principle to a high number. The max is 128 using the arrows.
These set the note triggers (nodes) very far apart.
Having a low bpm would also help
This assumes you have a sound with a long sustain. You can experiment with the Slow Violin in the Nodal Synth.
If you have an evolving texture with a slow attack you could retrigger it as required with node A going to node B and back. Using Absynth to test.
This gives the sound of infinite length.
If you set the note length in the node panel to a high percentage then you will to have some distance between the nodes to prevent overlapping of notes playing.
The continuous controllers in the edge panel could be used to fade in volume to smooth out attack phases on triggering.
Note: I only ran a few test over medium time as the long times can be long.