  Gaseous detectors are used in high energy physics as trackers or, more
generally, as devices for the measurement of the particle position. For this
reason, they must provide high spatial resolution and they have to be able to
operate in regions of intense radiation, i.e. around the interaction point of
collider machines. Among these, Micro Pattern Gaseous Detectors (MPGD) are the
latest frontier and allow to overcome many limitations of the pre-existing
detectors, such as the radiation tolerance and the rate capability. The gas
Electron Multiplier (GEM) is a MPGD that exploits an intense electric field in
a reduced amplification region in order to prevent discharges. Several
amplification stages, like in a triple-GEM, allow to increase the detector gain
and to reduce the discharge probability. Reconstruction techniques such as
charge centroid (CC) and micro-Time Projection Chamber ($\upmu$TPC) are used to
perform the position measurement. From literature triple-GEMs show a stable
behaviour up to $10^8\,$Hz/cm$^2$. A testbeam with four planar triple-GEMs has
been performed at the Mainz Microtron (MAMI) facility and their performance was
evaluated in different beam conditions. In this article a focus on the time
performance for the $\upmu$TPC clusterization is given and a new measurement of
the triple-GEM limits at high rate will be presented.
