many ask like this question and the answers are so easy

Event Ninjas may come and go in events but they usually comes back when the Community wants them .. Oasis collects feedbacks thru their Event Feedbacks Forms where players says their thoughts about the current line up of events of the cycle or week, along with that, they also ask in their forms about what ninjas or items you want to see in that events, at the end if you want to say more you can suggest freely like suggest "i want this ninja to comeback in events to this events", and if the majority of the community says and suggested the same Ninja or Event, then the possibility of having them back is greater ..

No one can predict nor say that this or that ninja may comeback as soon as next cycle but the assurance of coming them back in one of the coming cycles is possible ..

Thank you for responding my friend .... but how many weeks or months is the cycle ? is it a year ?

Event Cycles is the event per week, that is what i meant about the word "Cycle" as you will notice at News Section, each week's set of events is called "Event Cycle" ..

ok thank you.

Every week the events changes, its in Hot Topics.

The same type of event might take around 4 weeks to 8 weeks to be repeated.

Like for example Refinement Rebate or Sakura event reappear like once a month or 2 months?

There is no telling what ninjas will reappear in ninja related event. But every week different ninjas appear in different redeemable event.

You just have to stack and keep stacking coupons until a good ninja event pops in, since not all ninja events are cheap even if they appear.

But there will come one, like this Sakura event with Jonin Minato. I only spend 3.8k coupons to complete my remaining frags to get up to 80.

Something all active F2P can achieve. Keep stacking coupons, read the news sections every week.

Normally, each "Event Cycle" (Events per week) changes what is offered, whether it be ninjas, costumes, and power items. Ninjas and costumes tend to be cycled through so that those players who have not recruited it has a chance to recruit or obtain the pieces over time. I do highly recommend to also head on over to our "Event Feedback Thread" as you can definitely send us your feedback regarding what you want to see in future events. Feedback does not guarantee something will happen right away, but it does help our team understand what the community wants to see in future events.

~Jib

With this logic none knows anything in any situation and we would still live in caves hunting wild animals to survive like our ancestors 30,000 years ago used to do.

The newest vent ninjas are put on display less often the more the time passes. After 3 months they usually appear once in a while if you suggest them in the feedbacks.