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We present the results of 15 years of monitoring lensed quasars, which wasconducted by the COSMOGRAIL programme at the Leonhard Euler 1.2m SwissTelescope. The decade-long light curves of 23 lensed systems are presented forthe first time. We complement our data set with other monitoring data availablein the literature to measure the time delays in 18 systems, among which ninereach a relative precision better than 15% for at least one time delay. Toachieve this, we developed an automated version of the curve-shifting toolboxPyCS to ensure robust estimation of the time delay in the presence ofmicrolensing, while accounting for the errors due to the imperfectrepresentation of microlensing. We also re-analysed the previously publishedtime delays of RX J1131$-$1231 and HE 0435$-$1223, by adding six and two newseasons of monitoring, respectively, and confirming the previous time-delaymeasurements. When the time delay measurement is possible, we corrected thelight curves of the lensed images from their time delay and present thedifference curves to highlight the microlensing signal contained in the data.To date, this is the largest sample of decade-long lens monitoring data, whichis useful to measure $H_0$ and the size of quasar accretion discs withmicrolensing as well as to study quasar variability.

COSMOGRAIL XIX: Time delays in 18 strongly lensed quasars from 15 years of optical monitoring