When you have a problem that is really annoying and you learn that some people can have it for years, I think it is perfectly normal to worry that this might happen to you too. This isn't just the case for DPDR. I am not sure it can be useful for recovery, butit seems like an at least normal worry.
Then, my feeling
is that most people recover after a short time. Given it can take some people years to have a diagnosis or even just learn about the name of DPDR, I think it is safe to say that there are probably a lot of people who have it for a short time and don't even report it online like here. People who have had it for a long time are more visible, first because they are around for a longer time, and second because they have had more chance to meet a diagnosis or self-diagnosis.
For simplicity, let's say you have 90% chance for your DPDR to last 2 months, and 10% chance for it to last 5 years. So for the second group, it lasts 30 times longer, so people from the second group will stay around and post or be active for 30 times longer (assuming they stay active all the time, for simplicity), so you still have a lot of chances to meet them. A quick calculation shows that if you then meet 10 active people on this forum, statistically more than 7 will be from the second group, ,if you use these probabilities. That's survivorship biais ( Survivorship bias - Wikipedia
The other thing is that people can have vastly different levels of suffering caused by DPDR. My subjective impression is that most of the time, if it is really bad it won't stay for long (or at least it has little chance to stay that bad for a long time).