As others have posted, if you don't ever plan on selling this rifle, than what's the harm in shooting it?
If your plan is for this rifle to be passed on to your heirs and for them not to sell it, than what's the harm in shooting it?
If your plan is to pass this on to your heirs as and asset and not a family heirloom, something that they will sell, than that is a different animal.
The more valuable it is, the more likely they might be to sell it, taking it out of the family heirloom class.
All that being said, if, say 50 years down the road your great grandson has no interest in guns, and sells the thing, do you really care if he got $500 for it because it is a nice used gun or $900 because nobody shot it. I mean, the guy's dumping a family heirloom that you took special care of.
Now, if, 50 years down the road, your great grandson has an interest in guns, would'nt you be happier if he was using this rifle to teach his son how to shoot and nurture and interest in shooting for your great great grandson?
Take care of it, but shoot the darn thing. Heck, the government could confiscate all of our guns in 50 years, would you rather that they confiscated a mint condition rifle that you denied yourself the pleasure of shooting, and they wind up chopping it up?