Re the Antiques Roadshow "restore" comment .. in situations like that they are referring to specialised conservation restoration services .... People who will clean and conserve the item back to as close as its original state as is possible WITHOUT lowering the commercial value ... Not your neighbour Jack next door with a power washer and a rattle can of black Rustoleum 
As to the original question .. yep if its yours you do as you like with it ..If you want shiny and new , then make it shiny and new ... and has also been touched on , "Rare" ... is a word used far too often , most of our "toys" are produced in the tens of thousands ... Its only when you are dealing with small firms or really old examples where age and nautural depletion has reduced numbers to very few examples .
Rarity is also a tool used to market modern toys today ... a factory churns out 100,000 castings then they get painted 10 different ways and suddenly they are rare 1 in 10,000's .. ( ie still not really rare )
For me a litmus test is often "ePay" ...do a search if only one or two examples show up in a month or two of searches then MAYBE your item is rare-ish ... the amount of listings with RARE "xxxxxxx" pretty much demonstrate its about as rare as acne in an adolescent !
So pretty much if it was made in an American Factory anytime after 1930 there is a 99.8% chance it is not rare
So once again , if its for your personal enjoyment , do as you will !
But if you are collecting to preserve some sort of value for the future then clean carefully and preserve as much of the original finish you can ... there is no reason why you cant employ BOTH methods tho , originals are only original once , and repaints if they please you... are perfectly fine ( unless you want to sell them handsomely later )
