There are several problems with this approach.
1. My experience is that reoccuring villains are a rareity in D&D. PCs don't like letting bad guys get away, and they can be pretty efficient at preventing it. Also, few fights have non-combatant witnesses. Combined, this makes learning specific tactical information something that a villain is specficailly going to have to seek out, rather than hearing about effortlessly.
2. Knowledge of PC tactics has a definite "shelf life". Especially when it comes to spells. As the PCs continue to gain higher levels, they will adapt new tactics. The tactics used at level 3 may bear little relation to the tactics used at level 6 to the tactics used at level 9.
3. Even though you may know the PCs are the protagonists, the bad guys do not. They are unlikely to direct all their preparations towards defending against the PCs exclusively.
4. If the villain knows enough about the PCs to effectively prepare for them, he likely knows enough to attempt to mislead them, avoid them, or otherwise try to stave off a direct confrontation.