pen refills

I was given a really nice pen the other day.  

One problem: the ink had all dried up.  My friends found the pen and thought I'd like it and not want to see it end up in the garbage.  Right, they were.

So, off to the stationary store I go to find refills for the pen.  Found refills, ok, but the problem is, they are packaged as a set of two.  

Why would you need to buy two pen refills together, I ask?  The clerk said it was likely because it wasn't worth it for the manufacturer to package one refill at a time.

I would really rather have paid $4 for one refill than $8 for two.  What are the chances the other refill will not have dried up by the time I've used up all the ink in the first refill?  What are the chances I'll remember I have a refill for this pen when the first one runs out?  What are the chances I'll be able to find the other refill two years down the road... 

Will I still like this pen in two years?