A rubber grommet can lose required properties during storage or service through several aging mechanisms. Network degradation may contribute, but a sticky surface or color change alone does not establish its cause.
For sulfur-cured compounds, changes in the crosslink network can affect mechanical behavior. Other elastomer systems can also degrade under unsuitable conditions. There is no single cure-temperature threshold that prevents all later damage, and color alone does not establish susceptibility.
Follow the compound supplier's storage guidance and identify the actual heat, light, fluid and mechanical exposure in service. Investigate degraded parts using relevant tests and production records. Select replacements from documented requirements rather than assuming that a similar-looking part will behave the same way.
