I would be satisfied with 20 years for commercial use of recordings, zero years – or simply no actual enforcement of copyright – for personal filesharing. Filesharers deeply passionate about music are likely to collect a larger library of recordings than they could ever afford to purchase, especially if they come from a relatively poor country. (No, streaming services like Spotify don’t do it. As far as I’m concerned, if it’s not a FLAC securely preserved on my hard drive and backups, it doesn’t really exist.)