Referral earnings are mainly about luck. No point having 10,000 of them if they are "dead".
If you have 10000 and you don't have a single whale or big spender that's tough luck
On the other hand, a high roller lucky to use your refcode could net you thousands of buckeroos within a short period of time. I had a few, but on the wrong website.
I agree at least 5 high rollers are enough to keep the money flowing but it's not easy to refer a high roller they understand what you are getting if they are your referral, so be a good referrer and offer support so you can get whales as your referrals.