Further comments.

If you believe that league draw will group teams with similar quality and you do not want big challenge, I think it is not wise to power train your players or vastly strengthen your squad near season end.

Even if you like using rest packs to train players, I still think it is wise to ensure there are sufficient rest /morale/health packs for normal uses. If these packs are used for training, your players' qualities will be high but this does not mean your team will be stronger than your opponents. Besides, players with more stars train slowly. Manager of high quality team are difficult to replace or upgrade players because auction market may not provide players matching qualities of his existing players. I don't like this situation. In contrast, if packs are reserves for normal daily uses, they must help improve your chances to win matches.

I heard some managers will replace whole team in each season. Some managers may even attempt to lower qualities of their teams before season end so as to improve chance of good cup draw. I personally do not like this. Even if I can win all competitions in this way, I do not enjoy.