If you're looking for AA guidance, we can only say that yes - prices do fluctuate based on demand and competition. Buying 7-8 months out is fine. In your case an intl PE fare for April is usually not huge demand if it's to Europe versus going in June - August, for example. But every market/route will have variability based on a huge number of historical data points that go into the algorithmic pricing. With AA and some others, you can request a trip credit for a fare (except Basic Economy) difference if you see the price drop after purchase. That credit can be used on a future flight within a year.