Rik may not be about till the morning, JK, but I'll try to help.
The usage runs from 1st of each month, and does not carry over to the following month. If you join halfway through a month, you have the full allowance to use until the end of the month, then it will be reset again on the 1st.
As you seem to be getting good speeds now, personally, I wouldn't bother switching on and off, but if you do, you stand a better chance of getting a higher sync in the mornings. Rik will confirm the technical reason for that, but I believe it's because, generally, mornings are quieter on the Internet than evenings.
As I understand it, your profile on MAX is never actually 'fixed', as it can fluctuate according to line conditions, but if you have a stable connection, and your profile appears to be remaining steady, then you can probably assume that all is well.
Your throughput is slightly low for your profile, but that could just be due to traffic on the BT networks. try it again in the morning, if you're at all concerned, but other than that, just enjoy your connection!
