I do probate as well and I send at least 4 letters to each lead. All of the letters are a little bit different with a different approach: 2 letters are from me(that go directly to me and I use a buddy of mines name on the other 2(using a google number so I can track). I do it this way because if they call us both then we have the ability to play good cop bad cop. 1 letter comes from me the week I get the list and 1 with my buddies name on it 7-10 days later. I space them all out about 7-10 days. Every once in awhile I'll do a bulk mailing to the previous months leads. I strongly recommend putting a picture of you and your family/dog..Even something from a fishing or hunting trip if you live in an area where most people do that. Most of these people just lost a family member or someone they thought of like family so the picture of you, your family or doing whatever could show that you something in common. I've been doing direct mail since 2005 and people love to know who they are talking to. My best success has been a picture of me, my dog and an ex girlfriend. People love my dog! I stopped keeping statistics on which letter people respond to because I've gotten calls from letters that I mailed 8 months to a year ago. In direct mail, if you are consistent then you will get results. Every Monday I get my new list from the court house, scrub it and mail it. When a mother or father passes and they have 3+ kids, things can get ugly, the heirs will get greedy and it could drag out for awhile. So, there is nothing wrong with doing a bulk mail a few months after you get your list.
As far as the ones you don't hear back from...A lot of those could be the surviving husband or wife...Some may keep it as a rental because they grew up in the house. Who knows? Don't worry about them and just stay consistent...
Also, read the seller when they call. If they are emotional then talking about the deceased when you go to the home is, in my opinion, a bad idea. Don't be the one to bring it up.....Obviously, there are times when it could be a good idea to share that emotional bond but let them be the one to talk about it. I've found that not talking about it after the initial phone call works the best for me.
Lastly, I'm not sure how everyone gets there data for their probate leads, but getting them from the courthouse is going to be the most current/fresh list there is. I know a lot of companies that sell probate data but it's usually a few weeks or more old.
I'm an open book so anyone, please feel free to email me(on my profile) if you want to share some ideas. I only jump on this site here and there. It's a great site for info but I always found myself getting intrigued by what other people were doing when I already have a system that works great for me. Best wishes everyone