It's time, well, spent
When it comes to cycling through the winter, each of us has our own threshold. Some turn back as soon as their nostril hairs begin to get crunchy. Others head out in even the deepest freeze, going elbows-deep in the Bar Mitts, like they're palpating a pair of horses and pedaling off into the tundra.
Regardless, even the hardiest cyclist eventually encounters some sort of insurmountable obstacle to riding outdoors: driving sleet; 20-foot snowdrifts; a rapidly advancing horde of White Walkers... Any of these things can render the landscape impassible and thwart the resolve of the most determined cyclist.
It's at this point some of us consider riding inside.
However, before you break out the trainer and resort to the hamster wheel, it's important to think about what you're doing. See, there really is no such things as "riding inside." Oh sure, you can sit on a bike and pedal, but that's as similar to as actual riding as air drumming is to drumming, or twisting your wrist and making "vroom vroom" noises while sitting on the toilet is to motorcycling.
Indeed, unless you've got a velodrome in your house, the closest you can get to riding inside is rollers. But, really, even that isn't riding, it's just balancing. Essentially, the only difference between you on rollers and a trained seal is that nobody's tossing fish at you.
Of course, this is 2017, and now there are all sorts of ways to curate a virtual cycling experience for yourself. One of the more popular platforms is Zwift, which allows you to ride virtual roads and even participate in group rides while spinning in place in your home. Certainly this is far more appealing than the virtual cycling experience of yesteryear, which mostly involved popping in a World Cycling Productions VHS and doing an interval every time Marco Pantani attacked.
There's nothing wrong with virtual cycling, apart from the fact that it's an insidious form of behavior that is destroying the very essence of the sport. Racers used to keep sharp and build mental fortitude in the off-season by bundling up and meeting for group rides. Now the local cycling club has a "Zwift Winter Race Series" instead. At this point, they might as well move the entire race calendar entirely online. Even Strava (which admittedly I also used to think was destroying the very essence of the sport until I finally tried it) is glutted with people's Zwifting exploits. This is deeply annoying. If I wanted to interact online with people who spend lots of time in basements on their computers, I'd log off Strava and read Reddit instead.
Obviously cyclists aren't the only lifestyle athletes who train indoors. However, unlike, say, scuttling up a climbing wall or thwacking a golf ball into a screen, riding a trainer doesn't help you hone any essential skills. After all, you've almost certainly mastered pedaling and balancing by now. (Unless you're a triathlete, that is.)
As for maintaining a high level of cycling fitness all winter long, absolutely, you may be accomplishing that by riding inside. But why and at what cost? Do you really need to hit the tarmac at full speed the moment the first buds appear on the trees? Might some other seasonally appropriate activity enhance your fitness, athletic skill set, and fun factor in a way that chasing after another avatar in Lycra cannot?
If you're the type to subject yourself to intense trainer sessions instead of hitting the couch and binging on Netflix like a normal person, then chances are you're also the sort of person whose mind and body could really benefit from a good walk, even if it is through three feet of snow. Hey, maybe you could even try snowshoeing. (Just don't spend all summer stomping around in a bathtub full of cotton balls with a pair of tennis rackets strapped to your feet in order to train for it.)
And even if you can't stand any activity other than cycling, there are still far better bike-related ways to ward off cabin fever than by frittering away on the trainer. For example, have you ever built a wheel? If not, you're missing out on the insight and satisfaction that comes from gaining a tactile understanding of the most essential component of your bicycle. Building wheels is as integral to cycling as tying lures is to fly fishing, and do you think the wader set spends their downtime virtually fly casting instead of working on their knots? (Actually that could be exactly what they do: the truth is I know nothing about fly fishing.)
Either way, instead of churning away at a poor facsimile of cycling, try engaging in a contemplative, fulfilling bike project. Read a book, watch some videos, order some parts. Then crack open a beer and get to work. Maybe it's building some wheels, maybe it's installing a new groupset, or maybe it's simply attempting your first overhaul.
Sure, you may not be quite as fit when the snow melts, but you’ll find riding yourself back into shape is twice as satisfying when you're doing it on something you built yourself.