Triathletes are typically goal-oriented people. If your goal is to get faster, you don’t have time for traditional base miles this winter.
Traditional base training requires the type of athlete who can dedicate & tolerate long, boring hours of easy riding with the goal of slowly earned, incremental aerobic fitness gains. This is optimal for a professional cyclist/triathlete because it's a time to add in just enough of the long, slow, traditional riding to further their gains a little, or to simply spend more time riding to improve their body composition.
However, a typical, time-starved triathlete doesn’t have unlimited time to ride at a slow pace. The ideal plan for a time-starved triathlete this winter is a plan that compensates for the lack of big volume at low intensity for a plan that develops your FTP. This means that it’s going to be more challenging, more intense and you are going to have to get comfortable being uncomfortable. But, that challenge and demand will keep you interested and better results in a much shorter period of time.
If you ever experience a lack of motivation during base training, change your environment! Train with like-minded athletes in a welcoming, but competitive environment.
Bottom line, winter is not the time to get soft. Keep riding hard, keep going anaerobic and train smart.