i have been having an ongoing argument with a buddy of mine, and would like to hear your feedback.

the question is this: over the winter months, will riding on the trainer 45 to 60 minutes 5x per week be beneficial or harmful if you do the following -

-ride with a fair amount of resistance, cadence 90-100
-15 min @~21mph, 5 min downshifting a few gears to ~24 mph, keeping cadence around 95, repeat.
-once or twice kicking it up to ~27-28 mph for 2-3 minute bursts throughout the ride.

one side of the argument says any time on the bike is good. the other says doing the same thing over and over will be harmful when done for 3-4 months.

any thoughts you could share beyond yes or no would be great.

thanks