Appreciated. We will Most likely apply mid November to allow sufficient time. Just to confirm the correct form is FLR(M)?
Yes, FLR(M) is the correct form.
Though I would not advise applying that early - as I said (as per other people's experiences here on the forum), as close to November 30th as possible... for example, the 28th or 29th. or if you want to be really safe, I would apply in December, so you know that her FLR(M) visa will definitely still be valid when she reaches 5 years.
There's no need to worry about having enough time because if her visa expires before the FLR(M) is issued, her spousal visa status will be extended while the application is processing.