This is a fair enough argument but some goods and services you can only pay for via fiat. In fact most goods/services can only be paid for by fiat or credit. Inflation is going to be a thing at all if you are just selling the amount of BTC you need to make a purchase in fiat. I am guessing you mean exchanging for large amounts of fiat that you wouldn't be using in a few days time.
Exactly. You can't yet buy everything you need, or even most things, with BTC. So it's simply unrealistic.
Beyond that, you should follow a simple principle: if BTC is selling for more than you think it will be worth in the near future, sell high, and wait for the price to drop.