I had a coach for a few years (and sometimes he checks these forums) and it was a positive experience. I got a lot of good out of the relationship. However, I got to a point where I was not so much limited by fitness as by other things and those other things were not addressed very well in a relationship over a long distance.
There are indeed times of the year (e.g., base) when the relationship with the coach may not be all that necessary for somebody like you who has been down the seasonal preparation road many times before. Many coaches offer the possibility of a lower-cost/low-interaction plan for certain months of the year and then high-interaction/higher-cost plan for other times. You may find that beneficial as you are probably more likely to overtrain during an intensity period.
I would suggest that if you decide to go with a coach that you plan on sticking with that individual for a year or two so that he/she can learn about you: how you respond, your quirks, your hang-ups. It will make it easier to tailor the program to fit your needs better, IMO. If you are disciplined, then that's good because that's an important part of the relationship. That will make you the coach's favorite.
I do indeed do my own plans now. I don't go to the trouble to write out what I'm going to do on a daily basis 6-9 months ahead of time. I tend to think in generalized "blocks" (4-8 weeks) that will have a general theme to it (threshold development, anaerobic capacity, etc.) and then the weekly implementation will fit the overall goal for that 4-8 week block based upon the reality at the time (revised race schedule, work schedule, injury, motivation, etc.). I'm a power meter user and I will use WKO+, PMC and other tools to manage my weekly fatigue and training load in view of the short and long term goals. I will throw in some experiments occasionally for fun too.
I have been tweaking and tweaking how I do this stuff over the years and finally this year I have seen some major improvements in terms of my short-term power and the normalized power I can put out in mass-start races, both of which have been a bit of a hindrance for me.