Here is what I have learned over the years re buying certain things. It is better to have them and never need to use them than it is not to have them and then to need them. Fortunately, many test kits have expiration dates so we know when we need to replace them even though we never used them.
When I needed to have accurate regular test reading for a stained acid water tank I turned to digital testing. I have a couple of hand held TDS testers and then I got a continuous monitor for the Altum tank which gave me continuous temperature, pH and conductivity/TDS readings. Before getting that piece of equipment I tried using the pH testers. But I found them to be unreliable and a PITA as the probe needs to be kept wet using a special solution between uses. Once one is put into use the first time they need to stay wet one way of the other. Hand testers need the storage solution while the continuous monitor is always in the water.
While that continuous monitor cost me about $150, over the years it was actually cheaper than having to use GH and pH kits daily. Also the temp. display was a lot easier to read than an in tank thermometer. This was also one of several reasons I ended up using digital temperature controllers on a number of my other tanks.