I remember trying them when I first picked up the character and was like "man this is tough, I'll try something else." after trying them for an hour or so. A few weeks later I decided I would sit down and figure out what I was doing wrong. After struggling with them for an hour or so I broke it down into separate motions. String/ db1/ hold/ run. After doing that I got down the timing in about another hour or so where I was connecting.
Probably took a couple weeks before I did them in matches, but a lot of the time they were drops that turned into just block pressure.
About 2 months before I knew I'd connect any LRC 99% of the time.
So all and all I would say it was a good 3 months before they became second nature in all situations. IDK I think some people the timing of this game just clicks with, there are friends of mine who seemed to be able to do run cancel stuff without trying, then others who are still inconsistent. It seems like it just comes down to having that one really clean LRC then you know what it feels like, but who knows how long it will take before that happens.
Tips for learning them and generally getting better at them because it seems like people are always looking.
Break the steps down to get each motion in your muscle memory.
Look at exactly how far you need to run before you can connect the next string, some attacks it is further than you think, some you don't run as much as you stutter step.
Once you can connect them midscreen, learn how to do them in the corner. It is harder and will make the midscreen ones easy. Plus the difference in timing will make you have more control over the run part.
Even if you get mad, refuse to mash out the LRC. they won't be consistent until you are pressing them in a consistent way.
Learn things like the pseudo tick setup with b11LRCgrab, this will make you really fast.