I tend not pay that much attention to Amazon’s recommendations. Though if you have the time and space to do it, you can customise it to be more sensible for you.
ie. you can allow for manufacturer time, transit time etc and how long you want the stock to actually last.

However, a lot depends on how often you are actually able to restock, so what works for you, won’t necessarily work for me.

I am fortunately in the position, where I can reorder stock and have it within 48 hours, which means that I can get on sale, within about a week, depending on receipt of goods etc at Amazon.

I would say that on average, I hold 4-6 weeks worth of stock at any one time. It helps to avoid the highs and lows and make it easier to refill.

But if your bringing stock in from China for example and it takes 6-8 weeks to get here, you need to allow for that lead time. So you would probably want to be holding at least 3 months of stock.