Russell Anderson notes "best way to get very low power is to put the part in low power STOP mode or turn it off and wake it up periodically. "

Can you give me an idea of what time frame you mean? e.g. turn off 8051 and wake it up every second? every day? every tenth of a second?

[As a newbie, I am not sure if I am violating some rules here by questioning in the middle of someone else's question. If so, sorry.]