Not moving up from tier 18 to 19 this week?

I'm going to leave you to calculate the aether out yourself if you want to know with certainty, but intuitively I don't like your potential unless you start getting, say, 140 lift per battle (double Eir + two light-blessed units).

You might also find this helpful. I've found some errors in the calculations, but for a general sense of how hard it is to move up, it will do the job.
https://fireemblem.gamepress.gg/q-a/how-ar-uses-aether-consumption-manage-tiers-and-which-tier-youre-likely-sit

Guessing defense will be key again so you wont lose precious points to "raiders" lol, but laughter aside, if you can get 2 wins a day without any casualties and minimize points (20-40 maxed) lossed then you should make it say......... exactly 6 days.