  SFXTs are a new class of HMXB unveiled by INTEGRAL. They are extreme systems
characterised by very short outbursts (a few hours) and extreme X-ray
luminosity dynamic ranges (~10^{4}). Ten confirmed systems are currently known
and have shown parallels with both Sg-XRBs and Be-XRBs. Temporal studies across
all timescales are key to understanding both the place of SFXTs within the HMXB
hierarchy and the accretion mechanisms at work within the objects. Here we
present the discovery of a new 51.47 \pm 0.02 day orbital period in the SFXT
XTE J1739$-$302 using INTEGRAL observations. We also present a higher time
resolution study of the SFXTs SAX J1818.6-1703, IGR J16479-4514 and IGR
J16465-4507 using RXTE that shows newly discovered flaring activity.
