Although not ideal to say the least and perhaps I should have been more elaborate; I was operating under the premise no one around Id trust to do WC. Because of that, I would not use my eheim auto feeder.
Depending on tank size, topping off would help keep water level at a reasonable level and isn't suggested as an alternative to water change. We're talking less than ideal situation here given not much to work with and if I needed to be gone 3 months lol.
Sad but true, I know folks that feed there marine fish very little, dont change water for 6+ months. Fish are fine for the short term. And we're all more than aware WC is beyond just reducing nitrates.