When did/do you stop favoriting 4s to champ and instead favorite feeders?

Maxed feeders only provide I think 5 covers (either full or via shards), so I favorite them when I get in the 8-10 cover range on a 5* (but this still means occasional Classics pulls)

90% of 4*s you'll never use - personally I have maybe 10 4*s in normal rotation (out of 130 potential characters!)

So the answer is, you can change your focus on who to favorite as soon as you have all the metas. My strategy is usually:

1. Feeders for Meta 5*s
2. Feeders close to 5* covers or shards
3. 4*s that are close to LT or CP rewards
4. 4*s that have enough saved covers built up to give a batch of rewards at once (at least to 280, which will give you 2 LTs, or 1LT and 1 5* cover)

You will soon have more 4s with 13 than you can champ, so you will be in iso debt. So either favorite the few 4s you will use or favorite feeders. You don't need to favor to champ. Right now I have 40+ unchamped 4s with 13 covers, soon you will too.

I always favorite either ones I don’t have yet or whatever is closest to being champed. I’m a completionist, so I want to have everything champed eventually, even if it costs me placement or power.

I stopped favoriting for useful characters after i had the Polaris gang, Polaris counters, Chavez, Thanos.

Then i Favorited those, that had saved covers until they were champed.

Now i have Valkyrie as Favorit and will keep her because she feeds Thor.

Changing priorities to LTs and CPS usually happens when you have a meta team and most good ones champed well enough to get you maximum rewards, so you can start focusing on hoarding for 5stars.