I guess it depends on what you want to do with it. If it is a collectible you hope to appreciate in value then yes. If it is a rider you want to have fun with and pop down to the pub for a pint on or something, then as long as the price is factored in, who cares.
Mine was the daily transport for a Navy guy stationed in Europe back in the 60's and early 70's. Story from his friend I bought both of my BMW's from was that he pulled off the road one night to pee and a car tapped the cylinder head and cracked the case. Rest of the bike was fine. He sourced a new case and had the motor rebuilt. It has a ton of patina and I'd be way upside down if I restored it so I just maintain it, put modern rubber on it and ride it.
