This is actually where the open airy substrate helps you. You cannot realy overdo your watering. (Not fully true but for arguments sake..). So, if you are away for a spell, you could do what I did this summer: I have a microsprinkler system, which switched on twice a day, for 15 minutes. THis was enough to get all but the largest pot drenched. As we were having 35+C days at the time, the trees loved the intense watering & cooldown.
When I am home, I water as needed. But when away, I do overdose watering. With the open substrate you get very little standing water in the pots, so it is not an issue to for a limit period overwater. And if you get a hot spell, you can set the time to water once during the day if you are at work. When you get home in the evening, you add water where needed, or -better- you do this in the morning.
Yeah, some people swear by their fishtank / pnd filter water. I do not ave this so no experience myself.