You're probably aware of the term "repetition" as it relates to marketing. The more times people see your message, the better, because all those impressions eventually add up in your favor helping you build brand awareness and making prospects more likely to try your camp.
But the number of people you reach is not as important as how many times you reach them. If you're starting a new camp, you might be OK sending 10,000 postcards to 10,000 families to get the initial word. After that, you're better off (from cost-effectiveness and brand-building standpoints) sending 2,000 postcards five separate times to the same group of families rather than 10,000 families just once.
Sending a one-time mailing might get overlooked by the majority of those you send it to. In fact the average person might not even notice it. But if you send a postcard to the same person five times in a row, you can BET they'll notice it, at least eventually, and they'll take interest in your camp assuming your offer's intriguing enough.
(Regarding your offer, this is another post for another day. You can't just send out a postcard with you camp's name on it and a picture and expect people to care. You need to give them a reason to reach out to you. That means you need to offer something of value; it's the only way to get the most impact from you postcard mailing or any sales piece for that matter.)
Just to put my money where my mouth is, I recently purchased 3,000 postcards for a series of mailings I'm doing. Though my first temptation is to send all 3,000 postcards to 3,000 different people at once, that's not the smart thing to do.
The smart thing is to send 1,000 postcards three separate times to the same 1,000 families in March, April and May because multiple frequency equals maximum awareness and marketing effectiveness. So that's why I'm going to do.
I paid less than 50 cents per postcard piece including the design, printing, shipping, labels and postage - about $1,500 total. I'm hoping to pick up at least $15,000 in new camper enrollments from these three mailings, which I don't think I'd get by mailing the same 3,000 postcards just once. I think it will work because the postcard includes a good offer. I'll let you know how it goes.