Pumping on top of latching on demand will cause oversupply as you are stimulating for more milk production.
If you are prone to blocked ducts, I'd suggest you take lecithin to help de-clump the fats in the milk to minimise the risk of it blocking the ducts. Some mummies have thinner ducts, and would be more prone to have it too. Other than lecithin consumption, you can also use a wide toothed comb during a hot shower and run it against your breasts in general. This is to stimulate blood and milk flow.
You can pump in the middle of the night if you would like to build a stash. And you need not require a huge stash (it will lead to another headache on how to use them before they expires or storage issues). A stash that can last for a week is good enough.
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