I had kept my Millionaire for a long time, since it was my first game i bought. And more important that was the game that got me into pinball. I was 6 when it came to my camping on 1987 and i played it for the first time.
Kinda lost its magic for me over the years and i decided to sell it when i came to the conclusion i had not turned it on for more then half a year
so my advice. get over the sentiment and sell it