It really depends upon the topic. Still it’s a time consuming process, doing literature survey(what other people did), finding the mistakes and unanswered questions in that think about an innovative way to solve the problem and implementing that and proving that. Then writing and publishing that. It may take upto years. You have to be consistent and focused.
Research can take a while. When I do a behavioural experiment it can take about 3 or 4 months to the experiment ready. Then it can take almost 12 months to get the data from all the participant. Then, it is down to the analysis and writing, this can take almost 12 months to finish the work and submit it as a academic paper. So in total a bit of research can take about 2 and a half years. Sometimes this can take longer as equipment can break. I have one paper that took 5 years but I’ve also had some take only a year.
Generally, researchers will have two or three experiments running at the same time.