There is no safe zone really at the moment since I think BTC is going to range in a and will retest 30K support 2 or 3 more times.
For me, if it breaks below 30k levels, it's a clear sign that the possibility of a bear market starting is exponentially higher.
When it comes to upper boundaries, I will be looking at 37-38K levels, and see if it breaks above and finds support.
In all above mentioned crashes, we had one top peak, followed by a major 20-30% correction, followed by 2 lower high peaks and corrections then entering descending channels and eventually major bear market.
I am gradually selling some of the crypto I hold and will be leaving some to see if it holds 30k levels.
Not a trading advice, I could be wrong.