ずっと and しばらく: throughout a period and for a while
Compare staying somewhere throughout the morning with a request to wait for a while, without assuming permanence or a fixed number of minutes.
Throughout the relevant time range
In a time context, ずっと can mean continuously or all along. 午前中はずっとここにいました。 says that the person was here throughout the morning.
午前中 defines the morning as the relevant range. ずっと does not expand that statement into residence there since birth.
An unspecified length of time
しばらく means for a while. しばらく待ってください。 asks the person to wait for a while.
友達とはしばらく会っていません。 says that the person has not met the friend for a while. しばらく can also mark the interval covered by a negative statement.
Duration and the kind of statement
しばらく休んでから、作業に戻りました。 says that the person rested for a while and then returned to work. The number of minutes spent resting is not supplied.
ずっと安いです。 can use ずっと to express degree, meaning much cheaper. Do not apply the temporal use covered here to every sentence containing ずっと.
Does しばらく待ってください。 request exactly five minutes of waiting?
Show the answer and why
No. It asks for waiting for a while, without a fixed minute count. Wording such as 五分ほど is needed to make the duration more specific.