If protected they can last for ages. Keep pH electrodes wet - science suppliers sell a plastic storage bottle with an 'O' ring seal which does the trick. Radioactivity sensors, though they are not that much used allow you to create decay curves in 'real time'. Many brands of light gates use a lot of battery power so use a mains adapter even though it adds some hassle. Also if you obtain strange results in bright light, turn them round to point the away from it.
Insight data logging software - check the 'About' box in the menu.
Version numbers above 1.5 work better with most equipment. Philip Harris SensorMeters are identified more reliably, Data Harvest temperature sensors are calibrated to within tenths of a degree and smoother graphs are the result. Insight version 3 is not as exciting as you might have hoped. There are no analysis tools like average readings nor a bar chart to do discrete readings of say, different light sources. Use this for up to age 12.