Have cycled from Northern Europe to South Africa, crossed Europe several times and also crossed US, New York to California. Best way to experience a country.
Don’t have time? Try to do a quick one and turn it into an adventure. One of my most exciting trips was going from Southern to Northern Europe in just a week.
I recommend to pack lightly, and don’t spend to much time planning on gear and routes - just do it otherwise you’ll risk to postpone it again and again.. just do it.