Do you need to change the resistor when you change a blower motor

I have a 2012 Audi A4 and live in Maine.  Last week, I started hearing
squeaking noises coming from behind the glove box when my heater fan
speed was set to 4 or 5. (12 is the highest setting)  If I turned it up, the noise
would go away, or if I turned it down, and it was inconsistent.  Meaning it
wouldn't even do it on 4 & 5 all the time.  

I had a shop look at it, and they said it is the blower motor, which I
somewhat expected.  Here's my question.  Do you need to change the
resistor when you change the blower motor?  The tech told me that he
would suggest just changing the motor, since the resistor is $400.  He said
that either I'd never have to change the resistor, or eventually I'd have to
change them both.  Which would pretty much make changing the motor this
time pointless.

He seemed to be suggesting that I take the chance, and just change the
motor for now, but obviously if there's a significant chance I'll have to do
both in the next few months, it seems like maybe I should just do both now.
Although obviously I don't want to waste money if it's not likely.  So my
question is, is it common to change both of those items at the same time?  
Or do people generally only change the part that is failing?  

I don't know if this is relevant info, but until about a month ago, the car was
in milder climates, and stayed in a garage.  Now it's outside all the time and
in a much colder climate.  I'm really just planning on keeping it through the
winter, and will be getting something else within the next year or so at the
latest.

Thanks for the help