Pot odds - when to use flop-to-turn?

[vicePlayer 0]

Hi there! I've been watching poker on TV and become interested in learning more about the game from various online resources. I've read quite a bit but still have some clearly newbie questions.

One that I wanted to ask more experienced players relates to pot odds. There are all these charts about flop-to-turn and flop-to-river odds. I don't quite understand when I would use flop-to-turn odds instead of always using flop-to-river ones after flop.

E.g. if I have a flushdraw with 9 outs on the flop, and I am being offered 25% (3:1) pot odds, is that a long term winner or loser?

Thank you!