If your PMs are scheduled correctly, then you are doing just enough PM work to take corrective action before emerging problems significantly degrade equipment performance and/or interrupt operation of that equipment. This means that getting behind schedule on PMs increases the likelihood of equipment degradation or failure. Simply staying behind isn't a practical option.
Handling Preventive Maintenance (PM) Backlogs
Two main causes of PM backlogs are personnel changes and unplanned downtime.