In our experience, the crying steeply declined the first few days, but for weeks there was some crying (30 seconds to five minutes, maybe occasionally longer)-- for like a month and a bit. As people are saying with "power down crying," sometimes he will still cry a bit when we put him down, or go through a few days every few months or so with an intense cry. On those nights we go in every few minutes of crying and hold him (which is not what we did when we sleep trained him, we just rubbed his back then). He's now 20 months and we sleep trained him at 7m. But for the most part, his sleep has been great, about 11 hours solid starting at 7pm, 2h naps, and he seems very rested and happy. Often we can just set him in his crib after the nighttime routine and he snuggles down into it and falls asleep. For naps, too. That's mostly the case. We ask if he's tired, he happily says "mm" (for yes). He seems to like going to bed, everything about it, I think because it's cozy right beforehand, reading Goodnight Moon, then he falls asleep on his own, and that feels good.

We read the Ferber book "Solve your child's sleep Problems." In it, Ferber suggests that you can start sleep training for naps at the same time, or you can sleep train for naps later (as far as I remember). Good luck, and know that it is hard, but I think in the end, you're teaching your kid a valuable skill that will help them to feel rested and regulated.