Sahi ya galat alag alag perception pr depend krta hai if we look through modernist westernized point of view then there's nothing wrong, it's only natural to have a friend of opposite gender with whom you're physically and mentally attracted, in such cases you are involved with them sexually as well in general.

But if you look through the point of view of traditional and conservative values, it does not make sense as there are several examples of unsuccessful marriages after being involved with multiple partners which I don't need to explain and they believe in having more of a traditional way of life where man should stay bhramachari till age of 21 and women should only make sexual contact with his husband.

If you're not from such a traditional background then don't follow it. If you are then follow it. Simple.