How many new roots is enough new roots?

[PaxTea]

I love the sound of semi-hydroponic. I think it would be a good fit for me, because I can already tell that I have a tendency to hover and fret about watering. The fact that you can't really over-water would work in my favor.

I keep reading that timing is crucially important, that you should transition only when the plant is in active growth and putting out new roots.

That's cool, I can wait and be patient. My question is, how much new growth? How many new roots? Is one little nubbin a sign that the plant is ready to go, or do you need several?

I ask, because it sounds like you need to make the switch while the new roots are still small little things. You probably can't wait around too long, once you get that fresh growth.

Can anybody point me to a resource with some pictures of plants (particularly phals) that are in an ideal state for transition?