There’s not a set timeframe for research. You’re looking for answers to questions. Some answers you won’t even get until you do a test run and figure out you’ve got to make a few adjustments.
Even keyword research, the base for a lot of research, is something that has a random timeframe depending on if you’re looking for a topic set of keywords, a micro niche, and or just low competition ez keywords with low search volume.
TL;DR: Things take time.