Apple launches new watches every year during the month of September.  But the good thing about apple is that they will continue to provide software and other supports for many more years, which is missing in case of many other competitors. The latest version of OS is watchOS 10 and it is worth to note that Apple Watch Series 4, which was launched in September 2018 is compatible with watchOS 10, provided you have iPhone XS or later with iOS 17. Now coming to selecting the right models, we will to consider the price and the features. The newer models have more advanced features and capabilities. So if you are looking for a device with the latest technology and advanced features, it will be better to select the newer models. However if you are on budget and looking for a high quality device that’s still fully supported and compactible with the latest software updates at least for next couple of years , then you can consider the older models or Apple Watch SE (2nd gen).