Depends if no pain. Adult hydroceles do not resolve spontaneously, but you can wait for as long as you like or even forever it does not feel uncomfortable or painful. Should be checked with an ultrasound to exclude remote chance of tumor. George bernad shaw never had his knee length hydrocele repaired because he didn't trust surgeons and thus wore baggy plus4 pants all his life.
As long as you can.. If you're sure your hydrocele is benign and you can cope with its mental ; physical effect and inconvenience, you can wait and see as long as you wish. There is no timetable for hydrocelectomy.