Flood Control
Used it for more than 8 years,
Worked through the time permutations up and down.
120 annoys the prolific but kills the attention seekers and spam canoneers.
It's what works for us, here. The workload issue for volunteer forum mods has always been the critical measure.
Same goes for search settings - it's the one feature that has always brought the site to it's knees every (Moores) 18 months so we keep it well throttled back especially with google doing it quicker and with others paying the tab.
Regards
Rob