My view on long range flights is that as long as you don´t put others on risk (people and property) go for it if it makes you happy. The most I did so far was 2.2Km on open fields. I know it is unlikely to happen, but if your drone fails, and falls from >50m high on someone´s head you will probably have a dead body. So if you do, just do it as safe as possible and be happy !