I recently purchased a 15-1994. With the help of the wonderful site http://www.hifi-remote.com I was able to get everything working great with it. However, after speding all the time to find codes and program them to specific buttons, I don't want to lose them when the batteries go dead. Couple of questions:
1) How long do batteries last in the remote?
2) Is there a low battery indication of some kind?
3) How long are codes retained in memory if the batteries run out or I need to change them?

Thanks for any help.

The EEPROM that stores the upgrade data, macros, keymoves, etc in the 15-1994 is a non-volatile device. The data will be retained for years and years, even without batteries. For example, ReplayTV remotes are shipped without batteries, and the ReplayTV code is installed in them as an upgrade code (this remote uses the same type of EEPROM as your 15-1994).
You do risk losing your data to a static shock or other glitch, though, or to kids accidentally sending the remote through a factory reset sequence. This is one benefit of the JP1 hack - it lets you backup your remote as well as customize it in ways not possible through the buttons. See [Link: hifi-remote.com]

To answer your other question -- I've had my 15-1994 for maybe a year and am still on the first set of Radio Shack batteries I picked up along with it. My battery life is probably extended by the fact my backlight hasn't worked for months now ... :(

Do you realise that most of the time you can fix the backlight by taking the remote apart and then simply putting it back together again? I'm not kidding, this usually works, the contacts become mis-aligned or something.

Rob - definitely worth a try, I guess.

Guess I'm not one of the lucky ones. Took it apart, looked things over, put it back together and backlight is still kaput.