it will get to the point that Bitcoin will become very expensive and the advice of buying and accumulating now is good since it is called a future investment because those who even bought a long time ago have made a fortune from investing early
If it means current chances are like last ones to invest in Bitcoin, it's not true because we need Bitcoin to be a good investment asset in future too. Because if it comes to time when Bitcoin is too expensive and people are no longer afford to invest in it, it will be no longer attractive for the crowd as an investment option, that is not good for its value and price growth.
Fortunately with Bitcoin, it's fungible to a satoshi unit so people can buy either 1 bitcoin or some satoshi.
https://charts.bitbo.io/satoshi-per-dollar/https://hodl.camp/sats_per_dollar/