Sorry if this is a dumb question.  I have searched for an answer here, but can't find anything.  My question is, should you replace your propellers regularly even if they do not show any signs of wear or damage?  If so, how often? (after how many hours of flight?).  The reason I am asking is that it seems to me that my drone has become more noisy than when I first flew it.  It may be my imagination, or just the fact that everywhere is quieter due to Covi 19.  But if it is more noisy could it be that the props need replacing?

Hi. Thanks you for reaching out to DJI Forum. With regards to this query. If the propeller is scratched, deformed or damaged, please replace it immediately. It is recommended to replace them at least every three months. If you have further concern or inquiry, please feel free to post it here at DJI Forum, we are here to help. Thank you for your valued support.

It depends on how often you use them. I typically replace my props every hundred or so flights unless I damage them.