Anecdotal evidence from someone who is new to gritty mix this season:

I bought one from a good gardening center about four weeks ago because it was on sale due to fairly poor health. It was rootbound in very peaty soil with moss growing on top. It also was wilting badly within a few hours of getting it home. I discovered aphids on it, and used heavy spray from the hose to remove them. The next day, I barerooted it and transplanted it into gritty mix in a larger pot. After dousing it with neem oil because the garden center warned me it might also have white flies, I put it in bright shade for a week to recover from repotting.

Within three days, it perked up considerably. By the end of the week I put it where it gets full sun for six or more hours a day. Temperatures have been unseasonably warm here (in the high 80s and up to 97 last week), so I have been watering it every couple days and ferilizing it with Foliage Pro once a week. It's put on a lot of new growth, never losing a leaf, and now the leaves at the tips of the branches are starting to color up. Of all the plants I've put in gritty mix (about 20 different species, from herbs to clivias), this one has shown the most rapid positive response.