Hi,
It really depends on your degree and university.
I found with my undergraduate degree (Professional Policing), that i would either have quite large gaps (3-5 hours), or rather short ones (30mins - 1hour). I don't think i ever had anything back to back. In my first and second year I had about 12-15 hours of taught content per week, and in third year i had about 10-12 hours per week. My masters is very different and only have around 4-6 hours per week of taught content, as most of it is independent learning.
Timetables do change each semester, so you may have different gaps each time your timetable changes.
Good luck,
Suzan - Student Ambassador