I don't see planning and routine as the same thing, though I see that a routine would generally be dependent on some kind of plan, usually in the mind, and in my case often unconsciously created and carried out.
Routines are very helpful to me because I don't need to think - if a task isn't part of my routine, I have to think it through, which is sometimes easy and sometimes pretty difficult. I plan most non-routine tasks and projects very carefully to avoid making mistakes, and if a project is complex, the planning can be very hard for my brain. I'm aware of the waste of time and the boredom of it all, and often worry about and question my thoroughness, always trying to break out of the overpreparation trap, but with only limited success. Routines can bore me and I sometimes find myself changing them just for fun. It may seem odd for an Aspie to rebel against repetition like that, but the changes are usually fairly minor and I'm starting from a very low-stress position, and it's me who chooses if, when and how I make changes, so it tends to be a positive experience. The other thing about routines is that they're often about rather mundane activities, so my brain is likely to be more free to wander onto something more interesting while the menial crap is processed on auto-pilot. I have poor tolerance for boredom, though it doesn't always look that way from the outside, because I might be quietly entertaining myself in my own head while doing boring things.