Do you have a plan for keeping in touch with your existing customer base?
How many of your existing cutomers over the last two years are you still in touch with?
How much business are you getting from existing customers?
Do you know how much money you could have saved by keeping in touch with your customers?
Do you how much plumbing work you have lost (by not keeping in touch) from your previous customers?

Finally and most importantly, do you even want to keep in touch with your clients?