I’ve done it both ways. (Wrote a thing about it the all-at-once way here)
These days, I like to just do it in batches of 100 (which is manageable when I have some spare time), but as many times a day as I feel like. 100-300 a day knocks the total down faster than it seems. I mean, think about it, after 10 days that’s more than a thousand.
The main benefit is it sets you up for getting back into the flow smoothly. With the big-batch method, that results in big waves of RE-reviews that continue to come at you for a long time after.
It really depends on how bad you’re going to do on those reviews. Doing 100 reviews takes a really painfully long time if you’re at about 0% accuracy, but it’s not bad at all with 80-90%.
edit: I have to say this because it seems obvious but it’s totally not as easy as it seems - don’t do ANY lessons until you’re out of trouble with reviews. You will want to. It’s reaaaallly tempting. But don’t until apprentice AND guru counts are back to normal.