If power consumption is a problem and you need to exit "power saving mode" really fast, you might consider Maxim derivatives with their /1024 timer divider mode (one machine cycle takes 1024 osc. cycles as opposed to 12,4 or 1) - the oscillator is never shut down so there's no "stabilization phase" needed, the program is running all the time, just much slower, you just toggle a flag from within the program...
Also you might look up their "econoscillators", much faster power down recovery than standard quartz, unfortunately much worse accuracy so using them for accurate timestamping/RTC is not a good idea.