What are the most effective chain maintenance strategies for gravel bikes, considering the unique demands of mixed-surface riding, and how do different chain materials and coatings impact durability and performance in these conditions? Are there any specific cleaning and lubrication protocols that can help mitigate the effects of dirt, dust, and moisture on chain wear, and what role do chain wear indicators play in preventing premature wear and optimizing drivetrain performance? Furthermore, how do chain maintenance practices need to adapt when transitioning from dry to wet or muddy conditions, and what are some common mistakes to avoid when cleaning and maintaining chains on gravel bikes?