It depends on the person and their preferences.
I've been with my guy for over a year and a half, and I usually have sex with him every time I see him, but I only get to see him once a week, so that's pretty normal. However, sometimes we're just not in the mood and it can end up being 2 or even 3 weeks before we have the opportunity to have sex again. Other times we're just more interested in spending time together or doing other things together than just having naked fun.
As for the question of is it normal; sure it's normal. Different people have different sex drives, and there's nothing abnormal about it at all.
