Classical methods would have you drilling characters for hours upon hours of wasted time.
> It takes about 10 seconds or so to set an image in your mind of the scene for a character, then a handful of reviews over the following weeks. Then you never forget it.
There are in fact many people who have learned 4000+ Chinese characters, using this or other methods.
But after a few hundred kanji the system starts to get so complicated, with more and more elaborate and contrived mnemonics, that IMO it isn't worth continuing that approach. But that's fine, at that point you're already on board and can learn the rest from reading real texts.
(The negative of abandoning Heisig after the first few hundred kanji is that you also stop writing kanji at that point.. which adds to my difficulty of hand-writing Japanese)
Aside: Do you learn simplified or traditional? I learned traditional. I would have anyway because my wife is Taiwanese, but I advocate others to do the same because it is arguably the same difficulty if not easier. And going traditional -> simplified is tractable whereas the reverse is not.
Learning the Heisig method is similar: learning from a perspective of handwriting is easier, and you get the ability to read “for free.” It’s a better approach, even if you never need to write by hand.