Do you run a dropshipping business? Tell me the lessons you've lerned

I've been exploring the idea of starting a drop shipping store with shopify and oberlo.

I guess my main fear is that since most of the items ship from china it takes a while to arrive to a market like the U.S. I wanted to reach to the indie hackers community and see if someone has any experience with this.

• Do you get a lot of refund request due to long shipping time?
• Is is worth it to invest in advertising for this kind of business?

Thanks :)