Dittto^
I used to hose off undercarriage after every job, but I've been a bit of slacker in that regard as of late. I could spend a good hour or two hosing undercarriage. I do try to keep access hatch bolts clean in case I need to adjust tracks or change drive motor oil.
I do make it a point to hose it off quarterly. As for interior compartments, like engine and hydraulic bay, they are ALWAYS super clean. I have caught weeping leaks due to hoses or nuts loosening up (machine vibration loosens everything over time) because I keep those areas clean. Especially important to keep rads clean, especially in my machine, which isn't tolerant of hot days (full metal jacket with not enough venting on exterior body).
I try make sure I'm parked on loose gravel when freezing temps hit. If your on any wet ground, you may find yourself stuck when it freezes.
I can't say keeping undercarriage clean prolongs life of undercarriage...probably keeps rust at bay, as packed on mud becomes an incubator for rust formation. The only time I've had to do repairs on undercarriage is when I work extensively in muck...the sand/clay/silt eventually work their way into roller bearings and blow them up. And high speed turns on firm ground seems to wreck them.
And it is always a good idea to remove drive motor covers after working in heavy muck, and wash them off. I get a lot of corrosion in there, as mud packs in there and does it thing.