  Interface Region Imaging Spectrograph (IRIS) bursts are localised features
thought to be driven by magnetic reconnection. Although these events are
well-studied, it remains unknown whether their properties vary as their host
active regions (ARs) evolve. Here, we aim to understand whether the measurable
properties of IRIS bursts are consistent during the evolution of their host
ARs. We study 42 dense 400-step rasters sampled by IRIS. These rasters each
covered one of seven ARs, with each AR being sampled at least four times over a
minimum of 48 hours. An automated detection algorithm is used to identify IRIS
burst profiles. Data from the Solar Dynamics Observatory's Helioseismic and
Magnetic Imager are also used to provide context about the co-spatial
line-of-sight magnetic field. Of the rasters studied, 36 were found to contain
IRIS burst profiles. Five ARs (11850, 11909, 11916, 12104, and 12139) contained
IRIS burst profiles in each raster that sampled them whilst one AR (11871) was
found to contain no such spectra at any time. A total of 4019 IRIS burst
profiles belonging to 752 connected objects, which we define as parent IRIS
bursts, were identified. IRIS burst profiles were only detected within compact
regions in each raster, with these regions appearing to increase in size as the
host ARs aged. No systematic changes in the frequency of IRIS burst profiles or
the spectral characteristic of IRIS burst profiles through time were found for
these ARs. Finally, 93 % of parent IRIS bursts with areas between 1 arcsec^2
and 4 arcsec^2 occurred co-spatial to bi-poles in the photosphere. Overall,
IRIS bursts have remarkably consistent spectral and spatial properties
throughout the evolution of ARs. These events predominantly form within the
cores of larger and more complex ARs, with the regions containing these events
appearing to increase in size as the host region itself evolves.
