In reply to Osiris:
>Should each take coils of a different rope?
No just take coils with both at the same time, either one of you or both of you depending on how much you want to take in, or if one of you isn't carrying a bag or whatever. Having said that, just using one and then carrying the other for later use on hard pitches/for abbing is preferable if there's only one block of hard pitches you're going to use it for, it's just less faff. If you're constantly switching between harder pitches you want doubles for and then simulable terrain it'll be easier to leave them both on and take coils.
>What is the ideal length for simul climbing?
Totally depends on the terrain, basically the cleaner the face is the longer you can get away with. Longer being generally better imho, keeps more pieces of gear between you. Unless it gets too long and starts to impinge on your communication, which is really important when simuling. On a nice clean face I like 30m, but have gone up to 50m on occassion when reaching the end of a long pitch and then just deciding to keep going. On rough terrain where it feels like the rope is getting caught a lot maybe 10m, there's a lot of personal preference involved tbh. On scrambling type terrain you're probably just carrying 5m or so in hand coils ready to use if there's a tricky step.