Two weeks with the Ultra convinced me that targeting 18 hours of battery life for the normal watch is a big miss. Make it chunkier and shoot for 24 hours. I get most people only occasionally worry about charging midday, but there’s a big difference between “occasionally” and “never”
If you do anything even moderately battery intensive (e.g. sleep tracking, runs longer than five miles, cellular usage), consider this your permission to get the Apple Watch Ultra.
Don’t worry about the size! You (yes, you!) can rock it.