2. Know your audience.
These are two of the first things you're taught in ad school. All great ideas come out of the brand/product, and all great ideas speak to the audience.
Years ago, the brilliant Mark Fenske wrote the "14 anti-laws of advertising." Here's #9:
Skip the plant tour. Stay as ignorant as the audience. Otherwise you'll be as useless as the client. Clients know too much about their own products to be able to write a good ad; all they can do is shill. Though clients may not realize it, they're hiring us not because we're part of their company, but because we're part of the audience. When you know too much you always have the answer. You sound like an infomercial.
While I understand Fenske's point, I would say that you absolutely should take the plant tour. You should be doing whatever you can to learn about the product. Immerse yourself in it. Watch it being built. Talk to the designers or chemists. Read about its history. Travel to the corporate headquarters to understand the company's philosophy.
And then do the same thing with the consumer. As Fenske suggests, be the audience. Walk into the store, find the product. Look at the other products around it. Buy the product if you can. Use it. Use competitive products. Listen to consumers if you have the opportunity. Talk to people who love the product and people who hate it.
Insight and ideas can come from all of that stuff, and you should know all that stuff. The key, and what Fenske is really warning against, is to not get bogged down in it. Just because you now know all of this stuff does not mean it should all be included in an ad. What are you trying to communicate? What will move your target? It won't be a plant tour, but it might be something you learned on a plant tour.
So, by all means, take the plant tour.