On ne le répétera jamais assez : évitez les tueurs de tâches, surtout ceux qui le font automatiquement.

Contrairement à Windows, une pleine utilisation de la RAM sous Android est une *bonne* chose et c'est rarement la mémoire qui bloque, mais le CPU :

"The problem is that Android uses RAM differently than, say, Windows. On Android, having your RAM nearly full is a good thing. It means that when you relaunch an app you've previously opened, the app launches quickly and returns to its previous state. So while Android actually uses RAM efficiently, most users see that their RAM is full and assume that's what's slowing down their phone. In reality, your CPU—which is only used by apps that are actually active—is almost always the bottleneck."