for me use your old Windows OS to the last bit of its blood, ie when your productivity tools and hardwares cannot run in it anymore that inevitably you have to buy new tools/SWs and hardwares that only support new OS, that you already got acceptable profits from the old one. upgrading system in productivity or professional world is not simply upgrading the OS alone, they have to take into account tools/hardwares compatibility in the new OS. incompatibility means they have to spend another multi thousands dollars on new tools/hardwares, disruption in business process etc, not really good for healthy. this is why according to some people, some banking still stick with Cobol

but i can understand the reason. the Wannacry outbreak in hospitals using XP, they also have reason for it. if its simply upgrading the OS (given budget is allocated) and they can happily continue business tomorrow, everybody would have done so since the beginning, this some hobby grade people dont understand.
i repeat, use your old Windows OS to the last bit of its blood while you can, BUT.... with a big BUT... also make sure your system is secure by putting in tools by people who are in and care about the security business. afraid of virus, malware, worm, exploits? we have anti virus, anti malware anti worm anti exploits tools, go get it installed. the pro/paid version is not that expensive. for free version i recommend Avast Antivirus. sadly there is hiccup in the Pro version of Avast in WinXP that i have to switch to Panda, but the free version is flawless on my other nonproductivity/family machines.
and second BUT is... if you still dont trust your antivirus well, learn how to make your system backup, such as AOMEI Backupper, pros know their tools so they installed in after fresh OS install, and then make the backup, they paid expert if they dont know how but have the money, if they dont have the money they need to learn, otherwise they should get Murphy's Eligibility Award. when something peculiar happened, another outbreak, HDD cranked in read/write mode for no apparent reason, CPU is throttled while idle etc, should raise the alarm, if needed, formatting and reinstalling backup will take few minutes and then they can resume business in free of fear state. having said this, alertness need to be learnt, some basic computing and OS operation as well. computer virus is not like real virus, real virus persist in existence and no way around it, but computer virus are dead when you pull the plug, they are dead forever when you make fresh install. get another utility tools such as file logger or something, it will inform you when new files created in your system, i made one myself.
forget/ignore about people saying XP users are a fucked up users, they dont have a clue and XP users have reasons to stick, its our money and well beingness, not them. in fact, new Windows are the fucked up one, they cant get the Windows Explorer working right as it used to be... which is the backbone for some pro users. i have 7 and 10 license but my productivity system is still XP . its still can run nothing wrong with it, some Antivirus still supporting it. so i dont see any problem with Win7 for several years to come.