Splitting Kwikpen

In Australia we now have the Kwikpen (4 doses per pen) as the only option, and I have just started on 2.5mg this month.

The cost is $280 (AUD) for the 2.5mg pen and goes up from there. The 15mg pen is $690.

Assuming I store the pen in the fridge the entire time, can I simply get the 15mg pen, and inject the lower amount? (A full 15mg dose is 60 clicks; 10 clicks would be 2.5mg for example).

This would save a significant amount of money over time - but can it last that long / is it safe to use it like that?

I would change the needle each time. However, I have heard advice of keeping the same needle for ~4 shots to minimse wastage.