Good question. So what is rate of fire is too high in airsoft? Airsoftology's Jonathan Higgs tackle this question in an episode of his Q&A Mondays. This is one of the more controversial debates in airsoft after FPS/Joules limits. He also touches on topics of the lack of AEPs and competitive airsoft.
"Tippmann Mail Call:
1:32 - Why are there so few electric airsoft pistols?
4:13 - What is an acceptable maximum rate of fire (ROF) for airsoft?
8:53 - What are your thoughts on competitive airsoft?