In all reality...the only time you really need to worry about ivory ferrules is if the cue has gotten cold...like out in your car. If you walk in the door and start breaking with it immediately, you could crack a ferrule...but I don't think you get that kinda cold in SoCal..so you should me a-okay.
If your ivory ferrules have a fiber pad between the tip and ferrule...you'll be okay letting the tip get a little bit shorter, as the fiber pad is there to help protect the ivory ferrules.
In the grand scheme of things, replacing a tip is a relatively small expense when compared to replacing a cracked ivory ferrule. Just sayin'...
Lisa =====> breaks with every cue I own.
Rick Chudy told me the same thing, that an ivory ferrule (assuming it is properly made) will only crack due to temperature extremes. I never leave my cue in the car, even for a few minutes, so the cue always stays at room temperature.