How early can i get same day visa ext appointment

Hi all,
Just a quick question - Because of Tier-1 General visa extensions closing after April'15, i'm planning to apply for a extension early, sometime later this year as my visa is valid till Jun'15, i just need to know can i get a appointment for the same day visa extension process(about 7-8months before visa expires)??
(I think the last time i checked, one could only apply for a appointment 6 weeks in advance before the visa expires, has anything changed with that), if not will i have to send the application through Post(which i think has a lot of waiting time)

Please let me know if anyone knows or are planning to do the same.
Thanks!

Around 42 days.

Service standard has improved considerably, so go for postal as everyone is getting back within a month and sometimes in 2 weeks time.
Mine is also valid right now till June-2015, and i am also considering to go for early extension in another 2-3 months.