If you have a LOT of products you'll HAVE to delete pins. Pinterest has a pin limit. It was 10,000 pins but I think they increased it to 50k now? I've got more than 20k products across all of my Zazzle stores combined, if I tried to pin all my products I'd hit Pinterest's limit and never have any pins for my blogs.
I'm an author (Fantasy novels), and a content writer (the website in my sig here) the site has 10k+ pages (been adding pages daily since 1996) and every new page gets pinned. I publish around 4 new novels a year and so pins for that go out.
But then the bulk of my pins are me collecting other people's pins (mostly recipes and crafts that I want to make, so save them on pinterest so I can find them again easily)
In the end, if I used Pinterest just to self promote, I'd hit the pin limit in under a month. I just have way too many products (not just on Zazzle, but including my non-Zazzle career as well).
I find it's far more to my advantage to use Pinterest as intended: a social network; rather then using it for self-promo of my products. Thus rather than blasting everyone with lots of pins of my new products, I instead repin other people's pins, and share those of FaceBook and Twitter. I've got 100 boards and topics range from quotes I like to cute cat photos to gardening tips to my fave music videos. All my recipes collections are separated (tofu board, winter drink board, summer drink board, cupcake board, bread board, mac&cheese board, pizza board, etc) I think I have fewer the 5 boards that are self-promo. I have one called "Art by EelKat" that is for my Zazzle products, and one called "Books by EelKat" that is my novels and book release updates, and one that is "Interviews with EelKat" that is my YouTube videos about how I make my art and write my books, then one that is "Eelkat's vlogs" which is my vlog. So that's 4. Yep. Less then 5. Yeah, I've 100 boards and 4 are self-promo the rest are my collections of other people's pins.
People are far more likely to follow you and repin your pins if you act like a screaming fan girl loving on other people's pins, then if you just spam them to death with self promo pins. At least, that's what I've found.
That's why, every time I send out a self-promo pin, I then re-pin 3 to 5 pins by other people. I try to make sure my repin of other people's stuff is way higher then my pinning of my own stuff.
I'll do that until I get close to the pin limit, then, I'll go back through all my old pins, and anything that has "0" interactions I delete. Then anything that is outdated I delete. Anything I've lost interest in, I delete. Stuff that's no longer relevant I delete.