I tested this theory that Hoyas like to be rootbound and undisturbed with one plant and after about 4 years in a regular hanging plastic pot in the soil in which it was purchased, ended up with dead roots & a few cuttings I was able to save. Other Hoyas not subjected to this experiment have stayed healthy.
Roots need oxygen & moisture at the same time to function. Just air = shriveling. Just moisture = suffocation & rotting. Either will cause root death and desiccated foliage because the roots have been unable to deliver moisture. Having to let soil dry, as if ones' tropical jungle plant was a cactus, is an unnecessarily stressful coping mechanism for non-desert dwelling plants in soil without enough oxygen for the roots to stay healthy when it is moist and can lead to premature loss of older leaves and in extreme cases, dry shriveled roots/dead plant.
The ability of roots to be able to function properly depends greatly on the soil structure/texture, which can change over time. Potting soil tends to be very dense, mostly peat, with very little air in it. Any kind of organic ingredients decompose into smaller bits over time, and roots fill air spaces over time as they grow through soil. Replacing soil periodically is usually necessary to keep plants healthy because of these reasons.
Negative experiences in regard to potting-up, where an undisturbed root ball is placed into a bigger pot with more soil around it, vs. doing a repotting as described above, can give rise to old wives' tales about plants not liking to be repotted/disturbed. Potting-up a root-bound plant that has roots surrounding the outside root ball often lead to this negative experience because those roots had adapted to accessing oxygen around the outside of the root ball and surrounding them with more dense, soggy-but-airless potting soil will likely lead to suffocation.
