FIRE on £2,000/month — a serious savings rate.

£2,000 per month — £24,000 a year — is an aggressive savings rate that usually indicates a high earner (£60,000+) or a dual-income household with controlled spending. With 7% returns and £25,000 annual expenses, your £625,000 FIRE number is reachable in roughly 14-15 years from zero. Start at 30, retire by 45. The maths at this level shows the power of savings rate over investment returns: even at a conservative 5% return, you'd still reach FI in about 17 years, only 2-3 years slower. That's because at £2,000/month you're contributing more than half your annual expenses in savings — and the higher your savings rate relative to expenses, the less dependent you are on investment returns. At £24,000/year, you're exceeding the ISA allowance, so pension salary sacrifice becomes the primary vehicle. Higher-rate taxpayers saving £2,000/month into a pension effectively save at a 60% discount via combined tax and NI relief.