Response to your questions:
1. There are many postings like yours. It is not possible to predict how long it will take the flashes to stop. In some cases people have complained of flashes years after laser or cryopexy to retinal tears.
2. Yes you are are at higher risk than older patient because you have longer life expectancy and some of your vitreous may still be in contact with the retina and peel off later. Older patients more likely to have all the vitreous 'detached' from retina face.
3. Generally the advice goes like this: If the flashes change, get more intense, more frequent, you have showers of new floaters or loss of peripheral vision see the retina surgeon ASAP. If same old same old symptoms annually or as directed.
4. Only your retina surgeon can give you the odds. These cases are too unique to generalize.