Re. the 80 Minute memory retention question. If I remember correctly, the volatile memories' content, is maintained by a large capacitor - not a battery. This means that when the instrument is switched off, the capacitor will slowly discharge and eventually, there will be insufficient energy left in the capacitor, to maintain the memory content. This explains the limited back-up time of around 80 minutes.

I believe the design concept to be quite sound in this respect, since alternative long-term storage is also provided - Floppy disk, SD Card, possible Hard Disk expansion on some models and even a link to PC.....

There is another possible reason for using a Capacitor, rather than an internal re-chargeable battery, to provide memory back-up. Whilst a battery would provide virtually permanent back-up for the volatile memory - as it does in a PC for the real time clock etc. - these batteries do have a limited life. However, a Capacitor will have a much longer life than a rechargeable battery and should not require replacement, during the life of the instrument. Changing the battery in a PC is a relatively simple procedure, compared to doing so in some of the Keyboard instruments.......