moving pawns forward to the 5th rank if possible(as white)


Pawns are strongest when abreast. Also, Pawns get weaker and harder to defend as they advance. If you have a Pawn duo on the fourth rank, try to maintain it there.
Almost the only case in which I would run forward aggressively with my center Pawn duo is when I have a chance to catch the opposing army asleep and push them all the way down to the sixth rank. But that's a corner case.
Normally, Pawns at e4 and d4 will be stronger and more influential than Pawns on e4 and d5 or on d4 and e5... simply because the more advanced Pawns are harder to maintain.

Here's a counter-example; a situation where running forward with the Pawns (instead of holding the duo on the fourth rank) looks like the correct option:
Its generally more important to develop your minor pieces before you push a pawn to the fifth rank. However, when your pawn push forces black to move back his active piece to a non-active square your pawn move hurts blacks activity, shown in blueemu's example. There's also the advanced french and advanced caro-kann line which involves pushing pawn to e5.
You should push with a purpose, otherwise you should wait with pushing to the fifth rank.


Similarly, Black gains no advantage from snatching White's e-Pawn:

Pushing e5 weakens these two squares
Pushing d5 weakened these two squares.
Pawns on e4 and d4 controls four central squares.