I've not exceeded 1.2kms yet, but at that distance it's basically invisible to the eye, so I'm using the FPV feed to fly it. If you know the area you're flying, the FPV feed is more than enough to keep constant mental orientation. I often use the diamond on the screen to know roughly which direction to fly to return to myself, but in general I know well enough where the quad is in relation to myself and kept a rough sense of my bearings well enough, to know which direction to fly home in.
I've only once had to use Home Lock when I lost FPV feed and therefore also lost my bearings and became disoriented, but HL and pull back on the stick and she came right on back into FPV range, where I took over again. Oddly, the only time that ever happened was while I was only about 100m away, I got too many trees between myself and the quad, so poured on a heap of altitude and HL'ed back into range. I've never had a problem at the bigger distances.
But I'm yet to get anywhere near 2.5kms. I doubt I'll ever go beyond 2kms just for my own peace of mind. I get far too worried when I'm out at big distances.