While laboratory measurements give you some information about the process, online measurements will tell the complete story. You will not miss any information and decisions will be made on stable grounds.
This picture is based on real Nickel measurements for a period of 2 month. Seeing this picture, the engineer in charge immediately recognised the reasons for unstable process. Later the results could be compared and improvements documented.
Nickel measurement in Canada. 2 hours measurement frequency.
Vertical: concentrations 0-0.7mg/L Ni
Horizontal: Time and date 26.7.2018 bis 13.8.2018.
Result: The process engineer immediately recognise the problem and could stabilise the process. A stable process leads to higher quality and less consumables.