Its not as important to change out the water IMO, because I'm usually gonna throw the "sample cutting" away anyway. I just use it to determine the sex, and force it too ASAP. Sure, change it out once a week though, keep it clean. Treat it like any other cutting. Maybe even added a highly diluted drop of bleach every other day @ 1 ppm in the glass. Use your aero cloner if you want, and have multiple plants to determine.
I'll take whatever little branch I can get as soon as I can get it. I don't wait for the plant to become mature enough first to snip a cutting off, unless i'm being lazy with it, or not in any rush. More often than not though they do get big on me first, lol.
Sooner the better usually, otherwise you could be wasting time and resources on males, if that's not your thing.