Just saying “kosher for Pesach” is not enough
Read the ingredients yourself and use common sense. If the product contains a suspicious ingredient then do not buy it.
You should check EVERY time ALL year. Even if you’ve bought the item a hundred times before. Hashgochos change. Some even disappear. And heimishe firms can change certification agencies, too. If it’s a habit, you won’t need to worry about forgetting it at Pesach.
I was just at Walmart and I found on their Pesach products shelf actual chometz, graham crackers, that someone deposited there. People who do not know to check carefully might think that these graham crackers are kosher l’Pesach.