It's not all that hard to stick with a toolkit version for a couple of months (or to be honest, even a project lasting up to 18 months is no big deal.
That depends on the system. If you are doing iOS development, while 18 months is possible it's not advisable due to every new version of XCode (one major, a few minor updates every year) having more advanced tooling, compilers, frameworks... furthermore you are going to have to use a beta version at some point to test and debug your software on for un-released versions of iOS that you have to make sure you work well on before they are released.
I see your point, I was more speaking to the attitude of people that want to spend years without upgrading the underlying technologies involved in building and running your project... the longer you wait the worse the transition is, and like I said in the meantime you are also missing out on things that could have made development easier or resolved bugs you had to fix.