Extending AV

[liveone]

I am currently on an AV (4 years) and would like to extend it and have completed a settlement visa application.

Need to know the following

How long before my current visa expires should I submit my application?
How long is the settlement visa valid for?
Even though my children have AV in their passports; would it be possible to include their details as dependents on the FCO visa? (much cheaper)

[vinny]

You may extend your AV by applying for FLR(O) before your visa expires (190).

You may apply for SET(O) before your leave to remain expires, but no sooner than 28 days (4 weeks) before the completion of your 5-year qualifying period (192). Adults aged 18 or over also have to satisfy the Knowledge of language and life in the United Kingdom requirements.

You may include your spouse and dependants aged under 18 on the same form for free (194-199).