  We report on the analysis of Rossi X-ray Timing Explorer (RXTE) Proportional
Counter Array (PCA) monitoring observations of the $\gamma$-ray binary system
LS I +61 303, covering 35 full cycles of its orbital motion. This constitutes
the largest continuous X-ray monitoring dataset analyzed to date for this
source. Such an extended analysis allows us to report: a) the discovery of
variability in the orbital profiles of the X- ray emission, b) the existence of
a few (recent) short flares on top of the overall behavior typical of the
source, which, given the PCA field-of-view, may or may not be associated with
LS I +61 303, and c) the determination of the orbital periodicity using soft
X-ray data alone.
