"that is not a good way to use summoning scrolls since you will get them for just 7 days“

Wtf does that mean? if you use the rebate scrolls, it's no different than regular scrolls (other than the fact that it doesn't count toward the rebate)

The rebate generally coincides with one of the 20 scroll monthly week

I alternate between 20 + 20 (for the two monthly weeks) to get 3 rebate scroll (which I also use, so 23+20 in the end) and 100 + 20 during the two monthly weeks w/ 100 on the rebate to get max value.

First, week 2 always come with rebate, thou never the full duration. You need to watch for event news and wait until the last day of week 2 if you have to, but generally that's when summon rebate happens, sometime that overlaps with week 2.

Given that, let's say you get 70 summon scroll a month, and for simplicity sake, let's say you get them all at first day of the month (or, you can think of all the ones collected from previous month) Here is how you SHOULD use them:

+70 (70 remain)

week 2 during rebate: use 20 (50 remain)

week 4 use 20 (30 remain)

+70 (100 remain)

week 2 during rebate: use 20 (80 remain)

week 4 use 20 (60 remain)

+70 (130 remain)

week 2 during rebate: use 100 (30 remain)

week 4 use 20 (10 remain)

+70 (80 remain)

week 2 during rebate: use 20 (60 remain)

week 4: use 40 (40 remain)

+70 ....

Basically, when you have >120 scrolls during week 2, use 100, otherwise only use 20 during each of week 2 and 4. With week 2 usage always during rebate.

This will allow you to complete all the monthly quest AND give you, on average, the maximal number of rebate benefit.

Masuri 1.5 x 2 x 4 = 12 a month

survival breakthrough on average gives almost 1 a day, around 20 a month

seal ninja, about 1/10 chance, so about 6 a month.

sage winning side, this is pretty much pure RNG unless you carry your team, so about 2 every 3 sage, which is 2 per week or 8 a month

that's almost 50 a month already, just for being active. On top of that you will get some from events where the reward is random, like lucky board. so 70 a month isn't all that hard w/o spending any resource toward it.

Of course, some of those are level/power "locked". Breakthrough, for example, is level locked so if you are lower level, you have less node thus get less. And masuri 5 win certainly isn't for everyone. But that's the gist of it.

For this month, the use 20 monthly quest is only on week 3, so you need to reserve 20 for that.

Unfortunately, it seems the rebate have not moved, so that means it will be in week 1 & 2. So the two no longer overlap. Thou if you have 120+ scrolls, you can still take advantage of the rebate as that leaves you enough for the monthly.