We bought our CT200 used and took up the offer to extend the warranty by 2 years for £495 up to 2021. A year later the same offer appeared so we decided to extend for a further 2 years up to 2023. However, we recently received a renewal notice from Lexus Care. This related to the first extended warranty and ignored the fact that we had a further 2-year warranty already purchased up to 2023. We could easily have paid a duplicate amount but fortunately we checked as thought we'd already this. Clearly the warranty 'system' does not cater for early renewals, and why should they? It's not exactly theft, but it's not exactly honest either !
Be aware that these 'mistakes' can happen.