"Back when" there were real winters October was the start of Cyclo Cross season, nothing better for developing bike handling skills and confidence.
After 'Cross it was time to fit the fixed gear for Base miles, still doing that today.

X-skiing or speed skating were the outdoor activities that replaced cycling in the North, provided racing and were the primary sports for those who used the bike as their "off season" fitness tool.

We rode rollers, again excellent for calm efficient high cadence pedaling style, I'd do that rather than deal w/ some "instructor's" spin bike twaddle but I'm firmly Old School.
Still better than doing nothing.....

With HRM & power meters a structured program on a trainer will keep fitness up, I'll go out on the FG instead.

-Bandera