@milamy and @tampora are right. You know best how hard you find it to recall new words and how often you ought to review them to make them stick.
Myself, I sometimes have days of massive… uh, ‘planting’ (never really thought of it this way, despite the flower garden thing, lol) new words, and the next day an absolute ton of review to make them stick. Sometimes, I find I’ve been struggling with the review one evening, but when I try again the next morning I can recall it all just fine (as if my mind worked through them while I was sleeping, which is nice of it).
I would say that you want to avoid reviewing constantly, especially on completed courses (which I only do a basic 1500 hundred point rep on each day, to hold the streak, as I used to have a bad habit of ignoring (and forgetting) completed courses), simply because it takes up a lot of time and if you get bored from doing this, may demotivate you from learning new words on other courses. Now days I avoid making a course ‘complete’ – I always leave one word so I have to review it at least somewhat or face self-shame for losing the streak, lol – but never do hundred word review sessions on them.
If you are worried about reviewing too much, if there is such a thing, then think about trying to keep your words learned/points ratio on courses in a specific region. On courses I’m still learning, I try not to let mine slip from about three thousand points per word learned (though I know that on my worst courses, points per word is much higher, and ‘completed’ courses can’t really fit to this as you continue reviewing them even once you’ve stopped learning new words).
But seriously, it is all about how you learn best. If you think you can retain words but review less, then do. If not, review to your heart’s content until you feel it’s stuck.
The leaderboards are always going to be skewed at the top towards those who are happy doing repetitive, hardcore rote memorisation, rather than those of us who are just casual learners. The boards by no means represent how many points/reviews you should be getting in order to learn efficiently. To see this, you just need to follow a small selection of other users – though some will be the hardcore sort, you will usually find that on your ‘personal’ leaderboard, the number of points people rack up is much smaller. For example, I follow user/smutsigakläder/, who hits insane points each week and blows me away with his dedication; but I also follow @LangAddict and @MarshallLanguages, both of whom are more middling (mercifully normal) on that front (depending on the week).
Meh, I’m just rambling now (again). Sorry.
Just… don’t worry about it. The crazy point-getters will be crazy point-getters, and it has no bearing on your personal learning.