dependent visa question

[UKUK2020]

Hello,
I am in the process of filling visa applications for my wife and daughter. I have tier 2 visa which is due to expire in two years time. The original length of the visa was 5 years. My question is what is the length of visa I need to use for my wife as obviously I only have two years left in my own visa. Should we select 3 years type or 5 years type. If we paid for 5 years would we get refunded if they grant us a shorter visa.
Same question apply for health sure charge.