I’m a 66 year old and about to finished the Increase FTP specialized section of my automated Trainerroad plan at the end of this week. I do not race or have any events in the current future but would like to redo the Increase FTP workout plan, but based on info from a Trainerroad podcast it is recommended that I do a maintenance period using the Maintenance Automated Plan. So:
How long should I make the maintenance trainer plan for?
You should first take a break from training and allow your body to detrain. Typically, you do that for 2–4 weeks, but no less than 2. You need to shed fatigue and stress before you start again.
Personally, I then manually add an additional base block before creating a plan with Plan Builder. That has worked very well for me.
Hey there,
Nice work on wrapping up your recent training plan! 
You certainly don’t need to follow a maintenance plan in between full-length training plans.
Each athlete’s situation is slightly unique, and the best route for them depends on their goals, schedule, training history, etc.
We actually have a really nice Help Center article about this, which you may find useful. I’ve linked it below.
What we do recommend at the end of each training plan is some well-deserved rest. 
This can be as short or long as you feel necessary, but we generally recommend at least 1-3 weeks. This should entail only easy riding, and only when you really feel ready.
In your situation, picking up another general training plan after a brief downtime would be a fine option. If you aren’t looking to progress in the same way, but rather want to hold on to the fitness you currently have for a while, a maintenance plan could be a good option, though. Generally speaking, if you don’t have events lined up on your calendar and are taking little breaks between plans, you don’t need to worry about the maintenance plans, though.
Let me know if this helps and if you have any other questions about this.
Best of luck with your training! 