I reckon that for the minute amount of current they drain, it's not worth removing it. After all, if the alarm's disabled, chances are that your insurance is too. If the battery's in good nick anyway, it shouldn't really matter. While it's rare that mine's idle for a long period it started after 4 months of being idle (see "sick"), but was alarmed the whole time, first turn of the key, even with a relatively naff battery.

Leaving it on a trickle charge is surely a better way if you are gonna put them into hibernation?