I'm regularly investing a small cut of my salary on crypto and there is no specific plan for time of purchase or withdrawal.
The only plan I have is not to invest on shady/new coins and not to sell on loss.
I sell when I believe I have enough profit and invest that back to another promising coin.
Nice plan. It is very important not to invest money which you are afraid to lose. As for me, i invest 20% from my salary in promising coins or ICOs.