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We present the light-curves and spectra of 24 afterglows that have beenmonitored by Fermi-LAT at 0.1-100 GeV over more than a decade in time. Alllight-curves (except 130427) are consistent with a single power-law startingfrom their peaks, which occurred, in most cases, before the burst end. Thelight-curves display a brightness-decay rate correlation, with all but one(130427) of the bright afterglows decaying faster than the dimmer afterglows.We attribute this dichotomy to a quick deposition of the relativistic ejectaenergy in the external-shock for the brighter/faster-decaying afterglows and toan extended energy-injection in the afterglow shock for thedimmer/slower-decaying light-curves. The spectra of six afterglows (090328,100414, 110721, 110731, 130427, 140619B) indicate the existence of a hardercomponent above a spectral dip/ankle at energy 0.3-3 GeV, offering evidence foran inverse-Compton emission at higher energies, and suggesting that the harderpower-law spectra of five other LAT afterglows (130327B, 131231, 150523,150627, 160509) could also be inverse-Compton, while the remaining softer LATafterglows should be synchrotron. Marginal evidence for a spectral break andsoftening at higher energies is found for two afterglows (090902B and 090926).

The 7.2/3 Years Collection of Well-Monitored Fermi-LAT GRB Afterglows