Typically we do more riding in the spring / summer / fall than winter for obvious reasons.

Because both myself and my wife work full time, it is hard to find time to ride any time of the year.
We normally ride Saturdays and then one or two times a week after work which sucks because it gets dark, cold and we get home late and eat dinner around 9 pm.
I ride one or two days during the week at lunch about 30 miles, but my wife can't do that.
She has every other Monday off so I have arranged to take half a day off on those days so we can ride during the day a decent distance.
I am 58 and she is 60. I feel her fitness really drops during the winter because we are only riding one or two days a week and I feel like life is passing us by.
One option is for her to retire, but that would be a financial difficulty for us.
Another option would be to find a cheap used tandem and set it up on a trainer and maybe ride an hour after work a few days a week to maintain some fitness level.
Its been decades since i have rode on trainer and its soooo boring, but maybe better than nothing.
When we go on vacations we are able ride more and I see how her fitness level improves but then it doesn't last long.
Any thoughts?