Yes, Blynk can be disabled (and thus no internet traffic) or enabled via connection management commands, but how entirely depends on the methods used.
For example you could use a button in the App to disable Blynk… but obviously not do so to enable it (since there is no link anymore) but as long as you ensure your sketch keeps running when not connected to Blynk, via Blynk.config() and other check loops and so one then you could have a timer or other process running on the sketch that would re-connect to Blynk as required.