you know the answer but just want someone to confirm your thoughts.
its a long, very long ride, not really complex but it goes on a bit. all the same its a great days ride and you will be well knackered at the end. if its wet (pretty much guaranteed) it feels 50% longer, joy!!
so there you go, sounds like a lot of hard work and takes all day. you can mouse out and let others do their bit for charity while you sit at home and regret not even trying.
On the other hand, there are others on here doing it, cause theyve not wimped out. Check the posts meet up with others, get out and ride and enjoy. when you stop enjoying pedal harder to finsh quicker.
Good luck