If you want to store as many songs on a portable device as possible, but also want to enjoy the confidence of future proof lossless format, why not give WavPack's hybrid mode a shot? It allows you to encode a song into two files: one .wv file at any bitrate you set, and one .wvc correction file containing all the rest of bitrate data. When both files are present, it plays as a lossless format. If only the wv file is present, it plays as that bitrate. The only downside is that you need a portable device which support WavPack