O gets fed everyday basically, but i can back it off a bit to a couple times a week
He's old enough now that everyday really isn't a necessiity and he'll be fine while your away with the 2-3X weekly feeding.
As Callen mentioned earlier,you can put portions in little baggies so there's no waste and little worry about water quality.
Im going away for a whole month....planning to do a huge water change a day before
Doing a large water change at the last convenient moment will help greatly but don't feed right after doing it. If you will have someone to feed occasionaly start the schedule right then,if not then feed well the day before the water change.
My old job always involved being away 14-21 days (sometimes 6 weeks). No problems using those routines,as Melissa refused to do water changes too...and sometimes forgot their feeding schedule (2X weekly).
One last suggestion. If your lights aren't already on a timer,put them on one (or just leave them off). With no water changes the nitrates will slowly build (faster if being fed) and algae can really take off with excess "light time".