Rather than try to time the market, determine how much you can stand to loose. Rule #1 of Investing.
Then pick an entry point. $375-$400 is as good as it gets right now in my opinion. Yes it's been on a run but without understanding how bitcoin run you can't really understand gbtc and its run.
Also know that Asia represents about 90% of all bitcoin purchases. They buy coins to hedge against their country's currency. As someone points out. They are buying for a use we are buying to profit.
Trading here represents a very small portion of the market.
This is more of a traditional investment than most the pennies on OTC. Do what you feel is best for you and your portfolio.
Everyone has their opinion of this stick. Many treat it like any other penny. To me it's not.