How hard should a daily spot the difference puzzle be?

Hi everyone! I'm launching Gotcha Cat on Product Hunt on November 7. It's a free spot the difference game in the browser: every day a cat detective brings 5 new find the difference puzzles, and I'm still tuning the difficulty. Right now a day looks like this:

• 2 Easy pictures with 3 differences (45 seconds)

• 2 Medium pictures with 5 differences (60 seconds)

• 1 Hard picture with 7 differences (90 seconds)

Two questions for puzzle fans: would you rather have a steeper Hard case (more differences, less time), or a gentler daily set you can finish over coffee? And do you play spot the difference for relaxation, or as a brain training habit like Wordle? Any answer helps, thank you!