I use FI cleaners far more often than what it seems most people on here recommend, in addition to using nothing but Shell 93oct and Chevron 93/94oct (and 100/105oct race gas for track days, tuning, and occasionally will mix race gas with Shell/Chevron 93/94oct in anywhere from a 5:1 to a 1:1 ratio).
I primarily use Redline SI-1, but also use Techron Concentrate. I would say I do a full tank plus full bottle as often as every 500-750 miles (every 2-4 fill ups). When I replaced the injectors on my 328 with higher flow injectors for the SC install, they had no "gunk" anywhere and the screens were brand new looking, as were all of the seals.
In addition, the valves that were replaced all looked spotless. No carbon, no gunk, no varnish, no build up, nothing. Again, they looked practically new.
I don't know if this was due entirely to the cleaners, but I should mention that the two stations I use are the only two within 25mi of me that sell ethanol-free gasoline. This has kept my fuel lines free of buildup, fuel filters have no black gunk, and my fuel level sender is spotless.
If you want to do.the best for your.car, find an ethanol-free station. Use RL SI-1 and Techron as well. I have never seen a single issue from frequent use, on any car. I have seen countless issues in cars in which they were never used, however: constant lean AF ratios, sticking valves, and economy reduced by 25% or more to name a few.
Seafoam is excellent as well, IMO.