I think last year was the most golden opportunity time. But if you had not grave that time it will never come I think. Bitcoin will raised more in this year. Btc is now out of control to invest in it.
In my opinion, every significant drop in price of BTC is a golden opportunity to stack some if you have the money to buy them. Last year was the rarest opportunity for everyone to load up the cheapest of it but we didn't take it seriously..we could be seeing $70-100k if the bull sprints once more.