Early and often is not a good approach, especially in the higher cats, and if there are teams you’re wasting your time, as they will just use teammates to bring you back.
Second question: what makes you think you can stay away? And how far do you think you can go from?
All that aside, assuming you can: 50k in I’d start thinking about trying things and the reason for this is because there will be a general softening of the legs by this point. I mean all of this assumes things are still together at that point. So for the first 50 it’s about following moves rather than instigating them.
At the start of the race everyone is going to be capable of following moves, so you’re less likely to get away. After 50k it’s a different story. 50k also gives you a chance to assess who is who and which teams (whether in the same kit or not) are working to pull things back.
Ideally you want to go when your effort causes the most amount of pain, and is least likely to be followed.
Over the top of a rise and onto a flat, right after a previous attack is brought back, around the corner into a head or cross wind. You want to make the chasers work to have to bring you back, and to do that you want to use the terrain and wind to maximize things as best you can.