Continuity With Meditation Practice I have been practising compassion meditation somewhat consistently. I usually try to do so in the morning and in the evening. Somehow, I've come to view these two moments as 'ideal' in terms of meditation. But, when I skip a meditation session, I am afraid or unwilling to meditate outside of those morning and evening times. 

Would it bring more benefit to just meditate whenever possible, independently of a routine schedule? I feel like meditating during the day (other than morning or evening) will maybe affect my schedule, making my evening meditation 'too much'. 

In sum, is it profitable to meditate outside of schedule (or even disregard schedule) to compensate for skipped sessions?
I hate to sound too critical, because you appear to have a healthy meditation regime, so kudos for that. Having said that, adhering too strictly to a specific routine runs the risk of being silabbatupadana, i.e. clinging to a ritual for it's own sake.

Based on contemporary learning theory, more frequent meditation is likely more favorable for developing the dhyanas, over a strict routine, or having few session with longer duration, for instance. I wouldn't be surprised if the suttas reflects these findings.

To sum up: a scheduled routine helps, as well as meditating often, even when it's outside your regular routine.