Factors including how you're grinding, what’s your grind size is, and whether or not you have dialed in the grind size to the phin filter affect total brew time.
For Nguyen Coffee Supply phin filters, we recommend a fine grind size and a 2:1 ratio of water to coffee. For other phin filters, we recommend experimenting to dial in according to that specific filter.
For example, coffee that is too coarse will drip too fast. Using less than 2 tbsp of coffee in a 4 oz phin filter may result in a fast drip as well.