Why Time-Based PMs Often Fail — and What You Can Do About It

“We perform monthly preventive maintenance with an 80%+ completion rate…but our machines keep failing. We’re constantly putting out fires.”

If this sounds familiar, you’re not alone.

Preventive Maintenance (PM) is meant to reduce breakdowns and improve uptime and equipment reliability. But in many facilities, despite high PM completion rates, equipment keeps failing. Why? Keep reading this blog to learn the answer.

What’s Happening

Many PM programs still rely on time-based intervals – often monthly, quarterly, annually – and are measured by:

• % PMs completed on time
• % PMs completed vs. scheduled

While these key performance indicators look good, they don’t tell you if you’re actually preventing failure, reflect asset condition, or provide insight into the true effectiveness of the PM. In many cases, PMs are completed because we’re supposed to do them—not because they’re needed at that moment. When a maintenance team is at this point, the checklists become just that–a “pencil-whipping” exercise. Managers and teams are reluctant to admit this, yet many are silently nodding their heads in agreement.

Worse, when performed, these “monthly” PMs are often completed anywhere from 5 to 60 days apart due to floating schedules. That wide variability introduces risk—and missed early signs of failure they are intended for. Now to be fair, this is most likely not the fault of the maintenance team but rather the situation they are presented with. (More on that subject at a later date.)

Why Time-Based PMs?

Time-based PMs are still common for a reason. They are:

• Easy to implement – With some equipment knowledge, key tasks identified, and minimal time requirements, a busy maintenance manager can quickly set up a PM program and copy the structure across similar asset types
• Simple to track and report – i.e. 50 PM’s in the system, 50 PM sheets returned.
• Aligned with traditional workflows – “We always did it this way, and it works for us”

To be clear, time-based PMs are a good starting point—but they’re not a long-term strategy. They’re a placeholder, not a solution.

So, What Can Be Done?

Well, the answer to that may not be a one-size-fits-all answer and not every facility/team is ready for the ideal solution of predictive or condition-based tools. But that’s okay—you can still improve by shifting your current approach through one small yet impactful move: ditch “monthly” PMs in favor of a fixed schedule.

By breaking the year into 4-week cycles, you have a solid foundation to gain reliable information into what PMs matter. Additionally, it is easier to schedule based on a week number and day of the week versus the day of a month.

As an example:

4-week PM of 200Ton Hydraulic Press (task list excluded); scheduled every four weeks on Tuesdays at 7am. You will know that this IS scheduled every 4^th Tuesday 13x a year.

or

Monthly PM 200Ton Hydraulic Press scheduled for the 1st of every month.

In 2025, the 1st of the month falls on the following days of the week: Wednesday (3 times), Thursday (4 times), Friday (3 times), Saturday (2 times), Sunday (3 times), Monday (3 times), and Tuesday (1 time). Based on this schedule, 5 PMs are set for the weekend, which may or may not be possible. Now, scheduling with operations becomes more difficult…and leads to pencil whipping.

Going back to the fixed schedule, this creates a reliable structure to evaluate:

• which PMs are effective
• which ones need to be improved, and
• which can be eliminated.

Though this is not end-state, it is a great stepping stone to Preventive Maintenance Optimization — a foundational piece in many reliability strategies that, with the right support, can be achieved relatively quickly.

PM Benefits:

• Easier to plan and schedule
• Greater visibility for teams and stakeholders
• More accurate PM effectiveness data
• Improved reporting consistency

PM Limitations:

• Doesn’t reflect real-time asset condition
• Requires tighter schedule adherence
• Needs production/operations buy-in

While a fixed interval schedule isn’t perfect, it’s a practical foundation for more advanced reliability strategies. With the right collaboration and buy-in from stakeholders, you can quickly reap the benefits.

Ready to refresh or launch your own preventive maintenance program? Contact me.