This pattern conveys a sense of urgency or inevitability: you realize that continuing the current action is not feasible or acceptable anymore. It often implies that external circumstances or responsibilities force a change. The nuance is that while you might want to continue, you cannot afford to do so.

It is used in both spoken and written Japanese, but it carries a somewhat formal or emphatic tone. In casual conversation, you might hear てばかりもいられない as a slight variation, but てばかりはいられない is standard for N2.

The pattern is often used with verbs like 泣く, 休む, 遊ぶ, or 心配する to show that such actions cannot continue. It can also be used with いられない meaning 'cannot stay in that state', so it often appears in self-reflection or admonition.