Hi,
Thank you for your question.
I am self coached.
It is a lot of fun.
The hardest thing is to be objective about what to do. Injury is the big risk for that reason.
The best thing is that I do not have a plan, just a program. I divide the time in 3 to 4 weeks blocks and have an idea about what to do work in each one.
How I distribute it within the block is driven by my own freshness feeling.
I made a lot of mistakes in the past. I had a plan and tried to execute it no matter what. I got injured or, if lucky, could not absorb the training stress in an optimal way for sure.
I always have this in my mind now so flexibility and having some process goals and strict training principles in which I believe are the only concerns.
Having a coaching certification is something I see in my near future so I have been my own guinea pig. After a decade of mild falilures, it seems that I finally got somewhere.
I strongly advise anyone who does not have the intention to become a coach to get one if money allows.
Some of the jeopardys of self coaching are also felt if one just buys a general plan specially in running. Not that much in cycling or swimming.
Trying to follow a bought program strictly is something that frightens me. Running does not forgive inadequate training. Injury is always a sure menace if we do too much too soon or do not know how to listen your body. On the other hand, if one is too conservative, the fitness gains might be poor if any.
A coach brings individualization. A key point for running, swimming but maybe not as fundamental for cycling given the data we can gather from a powermeter (FTP,. Power duration curves, TSS, PMC, etc…). The data itself creates a great part of the individualization if one follows a modern training program.
So… If I wanted to upgrade my running with a fall 70.3 in mind,
1 - I would put my swimming and biking in maintenance mode until June
2 - I would hire a triathlon coach but with her/him focusing me in a 6 month running block
3 - I would plan some intermediate goal races and a half Marathon in the end of the block.
Maybe what you spare in buying the plan, pool time and bike maintenance can partially finance the coaching fee
Another thing, if you train 10 hours per week and reduce bike and swim maintenance to a 3 hours total, you can dedicate 7 to you running (including strength and mobility). It is already a very decent volume.
Just be sure of one thing. A properly coached and well executed high volume 24 weeks running focused program will change you running ability forever.