I used to do that with expireds and NODs. With a regular farming you have to do it for months consistently and be prepared that majority of those fliers/letters will end in trash. Unless you also have listings, open houses, neighborhood walks, benches, etc. ~ combos work the best. 

Good question, I know some around her to do this but I have not so far.

Val Evans has my favorite answer so far.  It's also getting the piece infront of the consumer at the exact second they're thinking about selling.  I know of agents who got listings in heavily farmed areas, simply because their one postcard showed up at the exact moment the person was considering selling.  All the other people's cards had been thrown out because it wasn't the right time.

Tony and Suzanne Marriott, Associate Brokers I have suggested few agents in my office - and they got about 3% response compared to other direct mail campaigns.

And direct mail piece needs consistency - at least 8 mails on regular interval (less than 3 weeks apart) I think.

Personally, I'd advertise on Facebook - and may have better ROI.

I am considering Every Door Direct Mailing... I look forward to more answers to this question.  Thank you!

I am thinking of doing it.

It's not in the quantity, it's all in the quality of your message. I suggest if you're seriously considering doing an extensive direct mail campaign, you find yourself a decent ad agency that can help you with your branding and can design unique tailored pieces that will specifically target your audience. Stay the hell away from whatever your company or a mass marketer is offering... unless of course you love throwing your money away. 

Why waste money mailing to people who might be renters or have no equity? I sort through the tax database and only mail to households where they have owned more than 8 years. This way only owners get a card. I send the list to my printer and they do the rest.

This last go round was 3 cards to 1,000 owners and one listing but it gets better the longer I stay at it.