[arch-general] Kernel upgrades question, as can't revert to earlier kernel

I've noticed for some time now that some distros are upgrading the current running kernel, rather than installing a new kernel version, which if there are problems with the new kernel, you could boot the earlier kernel, which you know was working ok. I'm currently updating my Don't Panic install, and there is a kernel update to 2.6.25.4-1 , and 21% done so far. Is there some way that this latest kernel version can be installed as a new kernel, and leave the existing one alone? I don't like this way of updating the kernel, as you have no way of booting to the earlier one if the latest version is problematic. 26% done now. Nigel.