whether to follow up after kicking the bishop

This is something I have been wondering about since the earliest of my chess-days.

If say, black, pins your knight to the queen with Bg4 early in the game and then...you decide to kick him away with h3 and he moves to h5...well...then the pin isn't broken, right? I mean I agree, you put a question to the bishop ("are we exchanging or not?")...but...what I really wonder...after the bishop moves, is there any reason not to follow up with the pawn-move g4? to gain tempo and finally break that pin? I am aware that in the ruy lopez main-line black does not follow up with b5 immediately after a6...but that's another issue related to opening theory...I am talking about pins that can occur after virtually ANY opening...so...once again...if you decide to kick the bishop, is there any reason not to follow up?

I think and hope I have made myself clear...thank you folks

keep it up with g4(g5)

It depends entirely on the specific position. There aren't really any general rules for this situation. 

Let's take your example above... Black plays Bg4 pinning the f3-Knight against the d1-Queen, and White has chased it back to h5 by playing h2-h3.

Ask a few questions:

Is Black already castled K-side while White is not? This would add some strength to the g2-g4 idea, since it could then form part of an attack on Black's King.

Is White already castled K-side while Black is not? This would make the g2-g4 idea more dubious, since it invites Black to open lines against White's King; either with h7-h5 or with a sacrifice on g4.

If both sides have castled K-side, will the enemy Bishop be locked out of play on g6 after White's g2-g4? This would require a well-supported White Pawn on e4 and a relatively static center.

Is White in a position to play N(b)-d2 then Nf1 then Ng3? This would break the pin without compromising your K-side Pawn formation.

so... u got it