Duration for dependant visa for GTV

Hi,
I am currently under the GTV and I have about 1 and half years left on my visa. I am applying for dependant visa for my partner, by default it is considering the entire duration.
Is there any way to apply for dependant visa for 1 year instead of the entire valid duration on my visa?
For the 3-4 extra months now I'll have to pay another 1000+ pounds otherwise.
Please let me know if this can be avoided and how to proceed or if this is the only way to do it..

Thanks in advance