You might also carefully consider your company's culture when deciding how to split your efforts between new (user-visible) features, preventive maintenance, and bugs affecting end users (especially any VIP end users that have your managers' ears).

For example, a 'Hero' culture rewards last-minute, late night, death march efforts, whether to fix an urgent problem, or to add that one feature that is (supposedly) needed to land a specific high-value customer/sale.