The 10-30 minute fluctuations are sometimes just me being inconsistent and then the occasional big change are schedule changes (my daily schedule is not the same each day) and then I am always trying to "move him back up" by 15 min increments, or move him later in anticipation of something coming up. But then I have another day pop up where I need to change times. I have skipped instead in the past when there is a big change in my schedule, but I hate to do it. For example, now I will be out at a training tomorrow night until 10pm or later, so his shot will be somewhat late. So I delayed it a little tonight and will again in the AM. Then, Sat morn, I need to leave by 8am, so I will try to edge him back to an earlier time by then...sigh.
His feeding schedule is also not set exactly. Lately, I have been giving a small snack every 3-5 hours, depending on his numbers. I generally know his eat/sleep patterns and try to work with those, but I set the timed feeder at regular intervals when I am gone and overnight. More frequent if his numbers are l