Ime discus keeping needn't be difficult. You can make it difficult by how you keep and feed them, but it doesn't need to be (that said I would have to have a very lightly stocked tank to only do 25% weekly water changes). As far as pH, there's a distinction between species in the wild that many discus keeping 'experts' don't make, which is that green and heckle discus come from low pH, but wild brown/blue discus come from pH varying from 6.0 up to 7.8, this according to Heiko Bleher who has spent many years in their wild habitat.
During the years I kept them I started at lower pH, that's what all the books said at the time. But with experience I learned this isn't necessary (I had variations of red/brown/blue discus, including wilds and some of the very early pigeon blood discus) and by the time I was in Florida with pristine well water at 7.6 I found they did great in that water-- which makes even more sense now in view of their varying native habitats. That said, I wouldn't personally keep them much over 8. My observation over the years is fish that can tolerate higher than their natural pH may do fine but not live as long if it's too much higher, though this varies by species. And if you want to breed them, discus tolerate higher pH than what is necessarily good for successful breeding.
As an example of species variance, without retelling the story, I found red head geos are tolerant of pH a good bit higher than guianacara-- so it does vary by species. Different species have different ranges of adaptability. You could simplify and say this graduates from comfort level to tolerance level to low level stress you may not detect (but can shorten their life-span), to a level causing distress or noticeable susceptibility to illness.
As a consequence, I prefer not to keep fish at or near their limits of tolerance. Someone can say I keep my discus at 8.8 and they're fine, but personally I wouldn't go there-- my opinion.
