Hi Paul,
Using the validator OR fxblue is fine for managing the EAs but once they are on demo I would recommend using fxblue personally.
As to your question about how regularly to change the EAs. I can only say what personally make the most sense to me at the minute and that would be to look at BOTH its performance over this life of its time on demo and a shorter period such as week and make your decision based on that. IIan in one of his courses uses a month and a week which is also sensible.
It would also depend on the timeframe as I would be looking to change M15 Ea’s more regularly that H4 EA’s for example.
Hope that helps.
PS Of course I hope you mean a mock live account (i.e second demo) rather than a live account right?