I do a quick net work calculation ~1 time per year. Since a significant portion of our net worth is still investment real estate, there is real uncertainty to the values on the asset side.
To those doing this more often:
Are you changing actions you take in your life because you have this information?
What insights have you gained from the process?
Doing actual vs what I've budgeted for (a variance analysis, if you will) is the big thing. In the plastic society we live in, it's pretty easy for a few $10-15 lunches (or $20-30 dinners) to add up quickly. Net effect is I'm able to plow more of my income back into my investment funds.