one of the forums I use, rixstep, specifically asks me to *not ever* put their password in my keychain (for ftp) because, they contend, that keychain has problems regarding the excessive polling of sites that resembles a denial of service attack.
so it is prolly a good idea to kill an old keychain. you might save bandwidth.
_________________________
macmini intel 2.0ghz, 2gb ram, bluetooth kb and wireless mighty mouse, OSX-10.5.6, 32gb ipod touch, itunes8.02, powered usb hub, superdrive, 120gb HD , lcd monitor. using xcode3.1.2 (with xquartz ) usb external 250gb HD w/ time machine, unix stuff & ilife08.FIOS router