Summertime heat + travel = dead plants

It happens every year. My Mom and Dad visit during Spring and Fall. My Mom who has the most beautiful plants down in Ecuador, buys new plants for my condo. Then she leaves and gives me all the instructions on how to take care of them, how often to water them, and how to talk to them.
It all goes well until I leave for a week or two. Then I come back and notice one is losing its leaves rapidly. then it dies. or at least that's what I think. Until my Mom comes back and miraculously resurrects it. Some times they are really really dead, so there is no use in doing anything.
I left just for 8 or 9 days at the beginning of June, and one of the resurrected ones died on me.. bad... It was so beautiful.
Now I am leaving on a Family Trip to Europe for 18 days and wonder if I'll find something when I come back. I hope so.
At least I know there is one that surely be alive and kicking when I come back: These plants never die! And I find them really pretty. This is the first plant I got when I arrived in Houston...so it has survived almost 6 years.. Yeah I guess I should ask someone to come water them once a week... but the only neighbor I know comes back the same day I leave.
(That is one of my secrets: Haven't even met my neighbors, or seen them! isn't that a shame??) I don't understand why we don't even coincide in the elevator or something...
Crazy