In the hands of a skilled pilot, the Excelsior is a screaming invincible war-demon for as long as its CR lasts. It does best in the middle of a crowded battlespace with lots of ordnance flying around; pirate and luddic path stations are perfect environments to practice with it, as there's lots of slow high-damage stuff like pilums, piranhas, and hellbores in those fights. I highly recommend giving it Heavy Armor and Reinforced Bulkheads so you've got more of a cushion for mistakes, as one bad overload can turn you into scrap. Expect to explode a lot while learning how to pilot it.