The present study concerns the search for ageing effects in 0.3 mm gap timing RPCs. Counters were made with glass and aluminium electrodes and kept under a continuous gas flow of tetrafluorethane with 10% sulphur hexafluoride, 5% isobutane and water at 10% relative humidity. After 500 days of operation at the saturation current an accumulated charge of 800 mC was collected, equivalent to over 8 years of continuous operation at 300 Hz/cm~2. No evidence was found of any long-term increase of dark current, suggesting that the ageing effect in timing RPCs is less severe than in streamer-mode glass RPCs. However, a visual inspection of the electrodes confirmed the existence of a deposit over the glass electrodes that was analysed by Electron Probe Microanalysis.
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