i was looking at my garage roof last week and noticed the felt has a lot of surface cracks on it. Is this something i need to rectify or indicative of its ages. I think its 10 years old but the roof dies not leak.
Up to you really, the life of a normal felt roof is reckoned to be about ten years.
A quick fix might be to paint it with a suitable bitumen paint to extend the life, I did use some paint for felt roofs years ago and it lasted well, no idea what it was now I'm afraid though.