Nothing wrong with reusing the water as long as it’s clean! I don’t know about the “on/off” capabilities of the “Pro”. My units are both older.
The only disadvantage I see is that when you start off with hot water right out of the tap your Anova will be ready to cook much sooner than it will be starting off with room temperature water from a previous cook.
I have reused the water for several days and several cooks without issue. Due to space limitations I use the water for plants when I am done. In the Winter I also add it to a heated bird bath I have. I too have older units and have not tried the pro.
How “hard” your water is may also be a consideration when it comes to leaving it in the water between cooks. I wouldn’t have a problem doing so at home as we have extremely soft water so I get no mineral buildup whatsoever. But when I travel to visit in-laws in California I won’t leave mine in the water any longer than necessary for the cook!