I think timing of flareups is very individualized. My easy child/difficult child 2 has been doing great since January, and I attribute it to hitting on the right medication combo (in fact, I've changed her from difficult child 2 to easy child/difficult child 2). My difficult child 1's mood has ebbed and flowed all spring, and I attribute that to some situational issues and to medication changes that made things worse instead of better (we're now saving some major medication changes for this summer so school is not affected).
What has made the most difference in the case of my difficult children is regular medical care. In our case, that means weekly psychiatrist appointments for medication management and psychotherapy (we don't use a separate therapist for therapy). It is only through this ongoing care that we have been able to make any progress at all.