For US-registered aircraft,
14 CFR 121.359 has required 2-hour recording since 2012. Most Airbus (certainly A380) also have 2-hour recorders. QF32 had a 2-hour recorder but the recording of the actual incident was still overwritten because it took so long to suppress engine #1.
It's easy to say "look at my new toy MP3 recorder that can record 10 years of audio". Your MP3 recorder isn't required to be certified under stringent regulations (which are there for a purpose) including being able to survive crash, fire, submersion at high pressure, etc., and emerge with readable memory. What's more, MP3 is very compressed; I don't know, but I expect CVR recordings aren't compressed because compression could fail and make the recording unreadable. Uncompressed audio needs a
lot more memory.
Having said that, the blame culture in many airlines, even among pilots, creates pressure to limit recording time and make recordings erasable. Even here on what's supposed to be a professional pilots' forum, the lynch mob was out for those CA pilots after their famous go-around at SFO almost before their engines had stopped. Fix that blame culture and you go a long way to making long-period CVRs acceptable.