I took off a bathtub wall spout fitting the other day and was surprised to find that the feed pipe that goes along the inside of the faucet piece was way shorter than I was expecting. This really spoiled my day as I was hoping in the not too distant future to replace the entirety of the tub and surround with one of those one-piece inserts, specifically so that I would not have to pull out the tub, redo the walls, etc etc. (edit: this is just an example. The question remains even if I wanted only to keep everything the same and just replace the tub spout, which, unsurprisingly, is not as secure as it ought to be.)
Are their any elegant ways to lengthen the pipe? It doesn't look like a sleeve fitting would be possible. But that means I have to open up the wall...and then, presumably, find a way to replace just that pipe, without having to rebuild the entire fitting it connects to. Which doesn't feel possible.
What techniques have others used?