Very intelligent question i wish i have the answer of your question but no idea if you got the idea or ways to prolong the plants when you are away from home please share with us.
For a more attractive version of the soda bottle trick, try "ollas." Google up the phrase "using ollas" and you should find both an urbanhomestead article with photo illustrations and a video tutorial on the topic.
Another cool idea is to bury wood in your beds. Google up "hugelkultur" and you will find an array of short articles that explain this technique.
A low-tech irrigation system with hoses works, too, if you can hire a plant sitter - I actually set multiple hoses off of multi-faucet faucet heads and typed up detailed instructions for the sitter to turn on the hoses - even to the point of how far to turn one faucet handle (from twelve o'clock to eight o'clock) so that a particular line didn't overspray the sidewalk.
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