To readdress the OP – doing progressively longer SS intervals will lead to more Time in Zone and more SS adaptations.
Using the TR plans you’ll never do more than a 30 minute interval or 90 minutes total. Doesn’t matter if you are just starting to ride a bike, a seasoned pro, your 1st time through the plans, or your 10th. But only you can decide if that SS ceiling is high enough for you.
Good luck! 