How much research experience to include on a CV? Do I have to include all of my research projects on my CV?  I have worked in ten different labs, mostly projects from undergrad, and most of my projects and publications are completely unrelated to my current field of research. I'm concerned that if include all my research experiences, people will not know what my current field of research is. I'm also worried since I am an early stage PhD student and my CV is three pages long and may be too long.

Should I include or exclude research experiences unrelated to my current field of study on my CV?
What you will soon realise is that there is no one CV to rule them all. More precisely, you will find that you need to tailor your CV for each job application etc, by (de)emphasising various parts of it. Getting a summer internship at McDonalds? Emphasise the hamburger flipping. Applying for a grant, emphasise the research. 

Thus how much research experience you include in your CV depends what you are planning to use your CV for. If it were to get a PhD position, I would say "Yes".

Publications stay. They always count.

Gradually, the research projects you did as an undergraduate will become uninteresting for your CV, for example, as you start filling your CV with new and exciting activities.  This always happens. When you are starting your research career, you will be asked to review papers. You can list what journal/conference you reviewed for on your CV. Later you will be on conference PCs or journal editorial boards. Then all of the reviewing experience will become irrelevant for your CV.