I found that spaced repetition really works as advertised, with software like Anki. However, it is not really suited at learning large amount of facts and concepts. If it took an hour to review your deck, it's not a good use of your time unless the cards are really high value.
For example, if I want to learn electronics, my time would be better spent on fiddling with circuits and learning through mistakes of implementation. The nice thing is that concepts are interrelated to each other, not discrete and decontextualized that usually happened with utilizing spaced repetition. You get much better value from learning through experimentation and retain it better.
Don't get me wrong, spaced repetition still apply. However, if you can learn something that will last a lifetime, you don't have to repeat it for a long time if ever.