Query for wife's Tier 1 General dependent visa extension

[Sillah]

Hi,
I have a question please if anyone can answer it.
I came to UK in August 2013 On Tier1 General (Dependant) visa as a spouse and after that my visa was once extended for 3 years and now my visa is expiring on October 23,2017 so my question is that can I apply for my visa befor 28 days ? How early can I apply for my visa extension? Because I want to be sure that my visa wont get rejected for Applying Earlier.
And please if possible send me a link from a proper source which states that visa can be extended earlier so that I'm completely sure because I couldn't find any.
Thank you.

[CR001]

On what basis did your spouse get ILR, 5 years tier 1 general or 10 years long residence?

[Sillah]

Yes 5 year Tier1 General. My husband has ILR .

[CR001]

You can extend your visa at any point before it expires. You will have to apply for a 3 year extension and pay the visa fee PLUS the £600 immigration health surcharge.

You can apply by post or in person for a same day decision.

[Sillah]

Thank you so much for the reply . It makes my situation very easy . Thanks CR00