FTFP interval length

I am currently in week 5 of the 18 Weeks of Sweet Spot plan and I have a question about interval length. I recently had shoulder surgery so I’m stuck on the trainer/unable to do group rides for my Saturday Sweet Spot Group Ride. So instead I’ve been doing long sweet spot intervals on Zwift on Saturdays. Then when I go to do my Tuesday workouts the interval lengths feel short.
Now I know that the obvious answer is just to FTFP, but is there any harm in combining two intervals to make them longer? For example, today would be 2x18 rather than 4x9. Any advice would be appreciated.

Stick to the 4 x 9 per the plan because the recovery period in-between improves the quality of your intervals. Allows you to recover better and sweet spot better.

Admire the willingness to make them harder but remember you are also setting yourself up for success the next day and the next day and the next and so forth by spreading out the training load with the 4 x 9.

I suppose if you were SUPER short on time you could skip the recovery intervals but I would not make a habit or regular occurrence of this


Thanks for the quick reply, I will continue to FTFP