Applying for Dependent without Main applicant ext approval

Hi,

I have 3 months before my tier1 visa expires , i am planning to apply my extension this week by post and for the dependents at a later point before their visa expires.

if i don't get my visa approval within my dependent visa expiry , can i apply for my dependents in UK.

The question is very much related reducing the amount of fee that i end up paying, given i have 3 dependents.

Thanks for your advice and comments.