Lisa, I do at least a half hour every night during the week. On the weekend, I try to do more just because I have more time. I try hard not to skip it. I used to do it in the morning, but it just took a bit too much time and effort, so I've substituted 20 minutes of stretching in the morning instead. I generally don't walk outside and do the bike on the same day, unless for some reason I have a lot of energy and extra time. The only time that ever happens is an occasional weekend.
My legs really don't feel heavy or bother me afterwards, because I can slow it down, or make it easier to pedal, if I want to. I've learned the hard way not to push it, and I've found the settings that are most comfortable for me. But if you feel like pushing yourself, you can. If not, slow it down. I can feel the difference the next day if I don't do anything, that's for sure.