Hydro Reading to gauge fermentation?

Do you do it?

I know it's the sage advice of the gurus to check gravity "three days in a row" to establish that fermentation is complete, But I never check until it's going into the keg, and that's only to calculate ABV. With the exception of an imperial or other huge beer, I doubt I ever will.

Yes and No.
I never test 3 days in a row. The 1st test is just a reference reading. The 2nd test would be wasted (unless it tastes really good). The 3rd test would only be 2 days after the first, so you would need a 4th test to check for a consistent reading over 3 days.
Most of the time, I can judge by looking at it, whether it's ready to keg, and I take a single gravity reading. If it's where it should be, I go ahead and keg.
Very occasionally, I find the gravity reading is high, in which case I postpone the kegging for another week or so.
There's also a lot of difference between kegging and bottling. If you keg before fermentation is complete, you can bleed off some CO2. If you bottle before fermentation is complete, you end up with over-carbonated beer or bottle bombs.

-a.

It is my opinion that the "3 days in a row" advice is for new brewers who are too excited and too inexperienced. It is solid advice so that they know when fermentation is done. As for the experienced brewers, I don't know any that actually do test 3 days in a row. Myself, I leave all of mine in the primary for at least 3 weeks, so fermentation is pretty much assured to be done anyways. I just take a hydro reading as I'm transferring. The FG is always within a couple points of where its supposed to be.