9500 -- power saving when there is no signal?

[inquirer]

The charge on my 9500 lasts comfortably through the day when I am in an area with a good signal. If, however, I spend a lot of time in the country where it is hard to find a signal or in the subway, the power drains quite quickly because the phone is constantly trying to find a signal.

My old Startac had a feature that put it into a power save mode when it couldn't find a signal within a certain number of minutes. (In that mode, it would search for a signal only every three minutes or so.) Does the 9500 have such a feature? (I couldn't find it in the manual.) If not, is there any solution other than turning off the phone when in a no-signal environment?

Thanks in advance