@Yi-Linda0 the smartest way to handle keys is probably to not have keys at all.
Many hosts find the most convenient this to have is a smart lock; guests can let themselves in and out without troubling the host, and there are no keys to forget or lose.
Some smart locks can program themselves automatically when guests make AirBnB reservations.
Search on this board for "smart lock" or on Google for "AirBnB smart lock". There are many options.
We had numerous problems with keys before too, so we no longer use them. We got this new lock a couple months back and we absolutely LOVE it! It syncs directly to my AirBNB calendar, sends guests emails with key code and instructions as soon as they book a stay, disables codes at time of check out (and accurately lol), and auto updates itself for me. I don't have to do a thing or have to worry about keys or anything myself, it's awesome.
Here's a link to check it out, I highly recommend it!