Well. Nothing like that is happening "in a few hours" when I play. Normal play for me is gonna amount to around 15-20 Arx per week. Then again I've been "just playing the game" which right now means mining as opposed to grinding out conflict zones, so who knows.I haven't been grinding for ARX and I've hit the cap every week. I did combat last week, which filled it pretty easily, but this week I've played only a little and I'm over 300 just doing some engineering and a material run out at Dav's.
It's not terribly hard and I only notice if I've hit the cap when I log in. If you're playing around the free ARX, that's a personal choice.
Either you've been lucky enough to "randomly" stumble into the particular combination of most lucrative activities, or you're lying, or maybe Frontier sets ARX award rates on a per-CMDR basis. The last one isn't so crazy - have you purchased ARX packs by any chance? Maybe people who purchase ARX packs are awarded ARX at a higher rate, if only for a time, to incentivize further spending?