Bitcoin supply is 21 million while the circulating supply according to several sources has reached 19.3 million or around 92%.
In theory supply and demand we know that prices will reach a height when the stock of goods is running low while the number of percentages of demand is high and for me this is the time to enter the stage of buying or collecting Bitcoins.

IMO, price circulation can be a view to analyze when is the best time to enter supply and demand.
The level of adoption of Bitcoin can be taken into consideration for us to find out the right time.