now many EA can I use on a sigle MT4 before having some stability/speed problems? 20 , 30 EAs?
Don't count on quantity, but on quality.
Pick your best 2-3 EA's and that is enough, in my case i have only 2 that i'm happy with.
Problems with load on EA's depend how they are coded.
yes, but my question was different. I have some EAs and I would like to apply them on different crosses and timeframes. How many "EA windows" could I use on one MT4 instance before to have stability/speed problems? Some time ago I read 20-25..
Impossible to answer. We have no idea how intensive your EAs are.
I have ~30 charts open with 30 simple EAs. Memory and CPU usage is in the noise. Your's could max out at one.