A divisible and fungible asset like a currency can never be "too valuable to spend", since by definition you get the value of the amount you spend. By virtue of comparative advantage, from
your point of view it's at most as valuable as the things you decide to buy.
What interferes with the spend decision of the holders are those pesky
deflationary expectations everybody rants about, and that somehow "don't apply" to bitcoin. If an asset is expected to rise, people will hoard it given the choice. It's only human to aim for realizing the gains of your most productive assets. You will always slaughter the old cow, not the gestating one.
For a non-productive asset like bitcoin the expectations are purely speculative (if they were technical the efficient market would have corrected the price up). So the correct title of the thread is
Bitcoin too hyped to spend: captures both the deflationary aspect and the speculative mania aspect.
Gresham's law does not apply because the government does not force a certain $/BTC parity (or anybody else for that matter).
I don't wanna go into a whole discussion about money supply and money creation again, but a constant monetary base ( = the 21 million coins) doesn't mean there is no (monetary) inflation.
for comparison, USD money supplies:

if you look at M1 (which is an even wider defined money supply than monetary base) up until 2008 when everything went to hell in a handbasket, you can see that the money supply of USD central bank money was constant, yet, there was PLENTY of inflation, price and monetary.
I believe the time scale is to small to actually see a direct correlation between the ~0% M1 increase in 2006-2007 and the inflation in those years. Just like deflationary expectations, there are inflationary expectations. People expect to have their paychecks increased yearly, and this eventually goes into the price of goods and services, regardless if no more currency was injected into the market. I think our old friend Milton would say that inflation is always a monetary phenomenon and if printing stops, so will inflation, eventually. So the 2007 inflation was made possible by earlier printing.