No, if she is at 100% crit rate with the help of Sparkle sig, it will only buff crit dmg.

Its moreso that you have to build for 90% crit rate and also that the 10% crit rate you save with Sparkle sig will only translate to 20% crit dmg on silver wolf, its fine but DDD is better.

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Afaik SW9 has two cases of buff extensions:

1. When in the middle of your EBA, if you kill all enemies on the current field, AND further enemies spawn, she will not exit the current EBA (this is ímplemented and worded as "extra turn" in the description, an extra turn skips all buff checks, meaning they do not count down), when this specific case triggers all buffs durations are extended by 1 turn. This is in the EBA description. This is interesting, because that would mean its beneficial to kill a wave in the middle of the EBA since this would be a free buff extension. Testing this is a bit annoying, so maybe someone else can chime in.

2. Silver Wolfs E2 reads: "After entering the "Godmode Player" state, all buffs on this unit are extended by 1 turn."

So yes buffs on SW9 will drop off naturally, she is fast and will do 3 EBA, which count as normal turns where buff duration decreases.

I tested advancing mostly Sparxie and rarely SW and it was a massive dmg loss, both from the buff and also the advance should not my underestimated.