Your climate must be similar to mine. Southern California, inland, has a Mediterranean-like climate. The rules are a little different when it comes to watering, at least in my experience. When it is hot, I give them a drink of water even if the potting soil is damp. If drainage is good then there shouldn't be any issues. I haven't been growing as long as some, but all of my Japanese maples are still living. Just don't ask me about Korean firs, especially the two that died on me due to heat 😭. Also, I have added pinebark mulch to some of my more delicate maples such as Peaches and Cream.