The longer you go without an update, the harder the time will be. Sooner or later, any actively supported project will have to switch to later versions, and the more versions you have to skip along the way, the more complicated and risky. If you update regularly, this becomes a fairly simple maintenance task.
, 2.1 → 3.0 , . 2.1 → 2.3.9 . , , 2.1 → 3.1 . , . , .