I am just going through 3 years of invoices and putting them into a booking software programme.
I had thought about going back further but I thought 3 years would be about right.
Three years or maybe more. I have custys that call me many years later than that although some will have moved address but 3 years is ok.
I tried mailchimp with the consent of the customer some years ago and didn't get one job.
Also I used to send out a letter, perhaps up to 400 customers in spring and before xmas but it was hard work in printing, envelopes and stamps.....but the work rolled in afterwards.
Typically, if you send out 300 or 400 letters to previous clients you will get at least £2000 of work.....that's in my experience, not to mention follow up work.
But now and probably the easiest method is to use Docmail. Keep all the customers that you want to retain on a database such as Microsoft access. Create your postcard in PDF format.....if it's Xmas, I use a nice snowy image and some words like ''Dear Customer, It may have been some time since you've had your carpets upholstery cleaned. It's a very busy period so be sure to book early'' etc etc. If it's spring, try some lambs or flowers etc......women like that.
Save your PDF file as above and then go over to Docmail....load your brilliant letter
and load up your custy database.
Then your stunningly brilliant post card (if your creative ) will be delivered within the week to your customers for less than the price of a stamp. If your good like me, you will see your postcard sitting on the kitchen side in admiration when you go to do the job
Funnily enough though I've seen my xmas card sitting on the side in the middle of summer when going to a job.