Picked up a mountain bike last Thursday.
Very different than my road bikes.
On the Road it is head down and go fast. In the woods you really have to pay attention to tire placement along with butt placement.(and what ever else I have yet to learn)
This will be quite a learning curve. There could be a little pain involved too.

I am almost in the over 50 Group. 50 years old in October.
My purchase was to allow me to ride with my daughter. She wants to ride a road bike.
My thoughts are that a few months on a mountain bike will help with conditioning without having to worry about on road issues.
Family time together etc. etc.

The more you ride your bike the less you will feel your age.