I have 2 Rheem units. They are heat pumps so they run year around. Since they are almost 10 years old I was wondering if I should replace the fan motors either in the outisde units or the blower motors. What is the average life expectancy of these items? I would hate for them to go out on a 100 degree day or cold day. I know for sure I can do the fan motor myself, done it for other people, but how dificult is the blower motor?

The blower on inside is relatively easy, Turn off power, Identify wires connections, Capacitor hook up. Then disconnect Wires, loosen screws on shaft holding squirill cage.
Remove 3? Motor mount screws. It is important motor rotates correct direction, usually reverse 2 wires(not the feed)on motor to correct. Should say on motor.

Thanks for your reply. What do you think about starting to change these out? I would hate for one of these to go in the middle of Winter on a Sunday morning. I have 4 of them so I could just do like 1 a month to spread it out a little.

Sounds good, Start with a not to critical one to eleminate discomfort while learning, and more understanding of what's required. Do one at a time, inside or outside to reduce problems if it doesn't work.
Direction is VERY important, reversing 2(not power), will change direction.
Turn off power.

I would wait until they go out. I have had them to last 16-18 years