Focus

[NoGamingInMississippi]

Is there any reason to have any focus on your war machine during your opponents turn? Can you shake off effects in your opponents turn?

[Hjelmen0]

No, you cannot use Shake Effects during your opponents turn. It can only be used at the appropriate step in the Maintenance Phase.

Whether or not there is a tactical reason for leaving focus on warjacks, you'll have to ask in the appropriate faction forums. Rules-wise there is no real reasoning; just that it is allowed, but cannot be used out-of-activation (barring special rules, like Shake Effects, and some feats and abilities).

[Ger]

The only model I can think of that wants Focus on him is one of the Retribution light jacks due to a special rule it has.

Otherwise any focus on a warjack at the end of a turn is due to just not using it on that models activation.