Do you ever find yourself going back to something you used to know well, only to find that you're now a bit rusty? In theory, spaced repetition would allow you to keep that knowledge from getting stale.

I think you'll find you learn new things quicker with judicious use of spaced repetition. As a bonus, you'll never forget those things as long as you maintain the habit. And we're all always learning, so that shouldn't be hard.

I do think the hardest part of spaced repetition use outside of the classroom is choosing what to memorize. In school, those decisions are made for you. I find it easy to bite off too much and start memorizing minutiae of a technology instead of the essential items. But I think it's just another skill to master.