It's a game, so some hand waving to simplify mechanics is to be expected.
This is purely speculation, but I do like to think that the labs will have collected all the necessary research data they needed before the item was sold. This would be things like photographs, field testimonies and other types of data collected via non-destructive means. Then it's all kept on a few pages in a yellow manila folder in a filing cabinet - as per the movies. The bulk of the research time is working out what it all means.
Also just to go on a brief tangent: I don't think the scientists and mechanics truly spend the amount of hours required to research or build the items they are working on. The actual work is probably only a portion of that, with most of the time spent on laborious administrative tasks, squabbling with other departments for resources and general day-to-day life while working on progressing said project. I'm only bringing this up due to an amusing anecdote I had at work where we had to bring in a few building management contractors and were given a quote of 4 man hours to complete the job. The task: move a small filing cabinet to the other side of the office. The work itself didn't take long, but all the clip on tasks like transportation and organising the workers do add up.