Technically speaking, that's not possible. I run 20 instances of metatrader from various brokers. Many instances just got halted with "common error" status after running for two days. All of them just got stuck with "disconnected" status randomly during the day.
In MT3 days (FXDD still offer MT3?), when Metaquotes supplied API, I used it to automate my system. It's not EA-based system though. My server runs for weeks on its own without any problem, as I coded the automatic reconnect function.
In a word, if you want always-on reliability, you should consider having your EA coded in actual compiled code (in c/c++, vb6, c#, or vb.net language) and used low-level API to automate trade and failover. Dukascopy, FXDD and Oanda provides API but may charge a monthly fee. If you're not into going extra steps, I suggest hiring some people to monitor for you. Yeah if you want it more affordable, you should outsource to India or some where outside developed countries.