Thermostats first
Heat failures cause more holiday losses than any other automation fault, so start where the risk lives. Check that each thermostat probe sits exactly where you left it, because probes knocked loose by cleaning read the wrong air and drive the heater wrongly. Turn each heat source off and on at the dial and watch the basking spot and cool end with a separate thermometer, since the thermostat's own display is the thing you are testing, not a witness you can trust. Replace any bulb that has been running close to a year; its output fades long before the filament dies.
Timers and the light cycle
Light timers drift, get knocked during cleaning, and silently reset after power cuts, so verify the cycle rather than the dial. Note the actual on and off times over one full day and compare them with the day length your species expects. Check UV tubes by age as well as by light: a tube can glow brightly while producing almost no ultraviolet, and a holiday is the wrong time for a marginal tube to be the animal's only source. Set timers to the wall clock's real time, not the approximation left over from the last clock change.
Misters, foggers and water
Automatic misters and foggers fail quietly, through a clogged nozzle, an empty reservoir or a kinked line, and the animal pays in humidity over days. Run each one through a full cycle and watch the spray pattern land where it should. Top up reservoirs to the brim, descale nozzles that spit unevenly, and check that drainage copes with the full cycle without flooding the substrate. If a sitter will refill anything, leave the water treatment and the measuring jug beside the reservoir, not in a cupboard they have to hunt through.
Alarms, cameras and power cuts
Decide now how you will hear about trouble. A temperature alarm that only sounds in an empty room is decoration; one that messages your phone, with the sitter's number as second contact, is a system. Test the alert by warming the probe in your hand. Point any room camera at the thermometer displays so you can read the room yourself from abroad. Know what survives a power cut, from battery-backed alarms to the thermal mass of the vivariums, and brief the sitter that a long outage means a visit, whatever the hour.
The two-day dress rehearsal
Finally, rehearse. Set everything exactly as it will run, lock the room routine in, and leave it completely alone for two days while you live your normal life around it. Afterwards read the maximum-minimum readings in each enclosure, check the humidity log, and confirm the light cycle matched the plan. Fix what the rehearsal exposed, then run one more day if you changed anything significant. Writing the rehearsal and each fix into KinsLe Care Teams as tasks, each marked complete with its time, gives you a dated record that the room was proven, not just intended, before the holiday.