Hi Dom, you ask "is this long enough?"
How long is a piece of string?
Depends what you want to do; you could easily fill years, many go back time and again, always finding something new. I feel that once you've got a taste of the continent, you may end up wanting more. Don't rush it, and I don't recommend setting a destination either. One way to reduce the pleasure of a break is to try to keep to a schedule.
It's going to be hot in summer; do a HUBB search for heat info, water consumption advice (er, drink lots) etc.
You'll love it