How much time you spend on niche and keyword research can vary greatly. For PPC campaigns, a great deal of importance is placed on the output and thoroughness of your keyword research. Therefore, the more time you put in, the better your results should be. I've found niche research much less demanding. Unless you outsource these tasks, then you just have to buckle down and put in the appropriate amount of work. How long this takes is different for each of us, but there are methods and tools to make the going easier, thankfully.
Oh really? Since you never spend your time on keyword research, how would you select your best keywords?