i'm at 110k power and still i don't see a reason to furthermore level it up from level 6. There are still for me better ways to increase power than spending 7000+ coupons there, but is up on what's your power and your relative levels.

Beware that ICEx there would suggest to me to go level 7, for example, but with the same 7000-7500 coupons that would cost me doing so i can get Exquisite Silk Cloth or an eventual new cloth that will appear, or to buy 72 ability scrolls and so to claim 9 purple treasure essences too as collateral effect, or even to buy 12 steps on page 10 for myoboku trial, all steps that grant me way more power with the same coupons spent than level 7 tactics.

You should always take a look at the coupon/power ratio of what you are going to buy.