There isn’t a specific period to determine how long we can feel the love towards another, it is not math’s, it just happens you will suddenly feel it and yeah it is going to be mysterious, and you will not know how and when that occurred “love comes when you least expect it”. However, everyone is different; some people can take months, and others can take years to fall in love, it depends on your age, experience and the way of thinking. However, for some people, it takes longer to feel that they are in love and that is because of many reasons, like a previous heartbreak that they are still healing from, they are practical more than emotional, or maybe they are none of the above. If you fall in love fast and by fast I mean It took you a week or a month, then you have to take care that what you are feeling is real and not puppy love or lust. However, puppy love always felt by younger people (platonic love) and it always fades away while a person is growing older; it rarely happens in adults.
If you are in love no matter how long it took you to realize that, you will know it deep in your heart. When we are in love, we will never hide out our true colors and we will always be ourselves with no filters or retouches.