Speaking from reader experience... When 50%+ of the "new update!" turn out to be KS or Patreon promos. Promos are ideally made together with an update, not instead of one, or readers will feel cheated. Once is fine, but I've had comics where update after update after update only was about a KS, and while I understand that it's a big, important thing for the creator, making the reader first excited about a new update and then only giving them what's essentially an ad is simply not smart.
But I have to say, there are so many great tipping comics! So many creators went out of their way to make it a fun bonus, and for that I'm definitely willing to throw tips their way!