TL/DR: How do you choose which units to spend for after you start to make it into the end game?

Today's 5* ex ticket netted me Kurasame. A decent Hybrid ice attacker. The problem is now do i go for his 7* or do i just let him sit on the bench like so many others. Which leads me to this question: What makes a unit worth pulling for once you have honestly reached the end of the game?

I have a decent line up, 7* i have around 10 of them, mostly magic chainers, but i do have other units as well. We all know the end game model for needed units if your at this point. Healer, Tank, Support. I have CG nichol, i have Basch. they function well for what i need and i have enough of CG nichol to get his STMR so i'm not hurting there. Provoke tank i have A. Rain(not 7* but i would pull for him to get it if a banner showed up). So for the most part i know other than a few trials i can easily defeat whatever content comes out.

So now that i have pretty much reached this point, How do i decide on what i should be putting my lapis and tickets towards? I know of two units coming soon (Beryl and Christine), both of which i will spend tickets and potential lapis. but beyond that i now feel at a loss. All i'm doing is collecting and not spending. I might drop a few tickets on a 7* batch banner to finish off say Loren, but really i could use some advice on what to do? And i feel I'm not alone?

So the question i would like to know is: At what point does a unit become a must pull here, once you have reached the end point? I feel this is a big enough question that goes beyond a simple daily help thread.