Most businesses replace computers when they break or when staff complain loudly enough. That approach costs more than it saves, and the cost is largely invisible because it's distributed across dozens of slow days rather than one big invoice.
Slow hardware has a real cost that never appears on a budget
A computer that takes four minutes to boot, three seconds to open each file, and drops video calls intermittently isn't just annoying. It's costing the person using it roughly 20-30 minutes of productive time per day. Three people on slow machines lose around 1.5 hours between them daily. Over a working year that's 300+ hours, worth somewhere between £5,000 and £9,000 in salary cost depending on roles, for three people.
That number doesn't appear on anyone's IT budget spreadsheet. It gets absorbed invisibly into the workday.
Then there's the support cost. Machines over five years old generate more helpdesk tickets: intermittent hardware faults, driver issues, compatibility problems with newer software. Each ticket costs time to diagnose and often doesn't resolve cleanly. Some IT providers will tell you this frankly; many won't, because an ageing estate generates billable work.
The Windows 10 deadline changes the calculus
Windows 10 reached end of support in October 2025. Hardware that can't run Windows 11 (a significant proportion of machines from 2017 or earlier) is now running an operating system that no longer receives security patches. Running unsupported software on business machines is a genuine security risk and increasingly a compliance issue for businesses with cyber insurance or certification requirements.
If you have machines that can't run Windows 11, replacing them isn't optional in the same way it was before.
Four to five years is the sensible threshold
That's the industry-standard guidance and it holds up in practice. At four years most hardware is still functional but the performance and support considerations start to compound. At six years you're typically paying more in support time and lost productivity than a replacement would have cost.
Workload matters: a machine used only for email and browser applications lasts longer than one running CAD software or large spreadsheet models. Role matters: a senior person's time is more expensive, so a slow machine affecting them has a higher cost than the same machine in a back-office role with lighter use.
Plan a rolling refresh, not a cliff edge
Replacing everything at once, which is the inevitable result of running everything to failure, creates a large capital spend, a major IT project, and often a chaotic period where new and old machines are running simultaneously with different software setups.
A rolling schedule of four or five replacements per year smooths that out. For a 20-device business, replacing four or five machines annually at £800-1,200 each means a predictable annual spend of £4,000-6,000, rather than a £18,000-24,000 hit every four to five years. It also means you never have an entire estate hitting end-of-life at the same time.