Its like lots of things, its as difficult and as time consuming as you want to make it.I was just wandering if it was easy to make acts and is it very time consuming? I'd like to have a go myself eventually one day
Simple activities running on green all the way with just a few opposing AI services can be knocked up pretty quickly. Once you start getting beyond that and trying to get your AI traffic to interact with the player with overtaking services etc the length of time can easyily go out of the window 
As a guide one of my one hour activities would take me about 25 hours to write and test. Sounds a lot but over the course of a couple of weeks of evenings and weekends isnt really. A 3 hour activity would take at least 100 hours, possibly even longer. Im working on one now for MidEastPlus which is looking like it might be a 4.5 hour jobby and so far i must have already spent 50 hours on it and im only 35 minutes into the activity.
Have a go
start slowly, dont try to do too much to start, keep it simple until you get to grips with it, then you can start expanding your skills. Its how I started, and im sure its how pete started too. and remember - the secret is to test, test and test again.
