As can readily be seen from the above definitions, LRT is not consistently defined, and is often confused with other frequently-used response metrics such as Customer Wait Time (CWT) and Mean Logistics Delay Time (MLDT).  Some organizations define LRT to include all the time beginning at identification of a failure or malfunction and ending upon the satisfaction of any logistics requirements--including personnel, spares, or any other need identified to correct the malfunction. It also includes corrective maintenance time. Others - such as the DLA definition above - are focused solely on the supply system.

Therefore, as with other metrics (particularly those used in a PBL environment), care must be taken to appropriately define the parameters of the metric and achieve a common understanding of that definition among the various stakeholders. As noted in the Product Support Manager (PSM) Guidebook, ..."these metrics must be mathematically and qualitatively described before they are useful." Additionally, also per the PSM Guidebook, they should be:

• Linked to system level required sustainment metrics objectives
• Appropriate to scope and responsibility
• Specify unit of measure
• Specify acceptable range or threshold
• Motivate desired long-term behavior
• Understood and accepted
• Easy to collect data and verify
• Readily assessed
• Analyzed to provide timely feedback

In summary, LRT is but one of many possible expressions of downtime and as such potentially may be used as an element of an Operational Availability (Ao) calculation. To re-emphasize, if used in such a calculation, LRT must be carefully defined as to what elements of downtime it includes and how it is measured, i.e., when the clock starts and when it stops.