There are some cards that I refuse to sell and will be unwilling to sell for a very long time. But for cards that are reasonably easy to re-purchase in the future or to downgrade if the prices remain high, I am selling.
Unless you are completely set financially (and this means something different to each person), it is borderline foolish and selfish to not sell anything in this boom. Collecting requires some level of sacrifice, either to further another collecting goal or to make our life and our family’s lives easier when opportunities present themselves.