Scatfast, I am new and I am attempting to use the indexing valve. I hope you weren't reading my thread, I have no idea what I'm doing.
I know a lot of my questions and communication have become additionally complicated because of the indexing valve. I believe in hind sight it would have been a better idea for me to use normal siphons and GB/FT ratios and then "upgrade" or test a less common method later on down the road. Remember simplicity is a beautiful thing in life when it means it simply works and in this case tested by the masses.
The biggest long term issues I've read about are related to impeller wear from power cycling. It might be normal to replace your impeller once a year. There is a member here who I read a lot of writing from about the subject who attempted to use a timed actuator to divert a single, always on pump, between two indexing valves to avoid power cycling her pump.
I insisted on using an indexing valve mostly because I love gadgets and as a computer nerd the indexing valve seemed to offer additional control, but really I've added more points of failure to a system that is already loaded with variables and needs some age, tweaking and maturity to develop fully.
Also about clay media, I thought I was buying the best of the best at first. I realize now the first brand I chose "Plant!T" floated. And the second brand I bought "mother earth" has some PH issues. So really I paid heavily for a product that offers little more value to me then cheap or free river rocks. My media has been by far the highest cost (embarrassed to admit how much) in my system, especially because the indexing valve means I'm using 6 times as much media as everyone else.
At least I can say everyone warned me and I went into my purchase and design with proper warning and understanding of the additional challenges I was creating for myself.
PM me the title of the book you're looking at, I'm curious, especially if it has stuff about indexing.